The Ukrainian capital was targeted by a "massive" Russian drone attack, Kyiv Mayor Vitali Klitschko said on Telegram early Sunday. 

Klitschko said the fresh assault left one person dead and another hospitalized.

"A 35-year-old woman was hospitalized, a 41-year-old man died," Klitschko said. He also said that the drone attack caused a fire in Kyiv's Holosiivskyi district, adding that it was contained.

The military said the attack was the "most massive" in terms of use of the Iranian-made Shahed drones. Security officials added that 52 out of the 54 drones launched were shot down by air defense systems.

Russia has frequently used Iranian-produced drones to attack Ukraine. Iran's supposed involvement in Russia's invasion has led to worsening ties between the Ukrainian government and the Islamic Republic.      

The latest drone assault on Kyiv came as the city celebrates the anniversary of its founding 1,541 years ago.

The anniversary, known as Kyiv Day, is marked on the last Sunday of May. 

Here are some of the other developments concerning Russia's war in Ukraine on Sunday, May 28:

Zelensky hails 'heroes' in Ukrainian air force

Ukrainian President Volodymyr Zelenskyy praised the Ukraine's air forces after Kyiv was struck by a Russian drone attack.

"You look up to destroy enemy missiles, aircraft, helicopters, and drones. Every time you shoot down enemy drones and missiles, lives are saved...," Zelenskyy said, addressing the Ukrainian air force.

"You are heroes!" the Ukrainian head of state added.

Ukraine's Kostyuk booed at French Open

Ukrainian tennis player Marta Kostyuk was met with jeers and boos when she refused to shake hands with Belarus' Aryna Sabalenka at the French Open.

Belarus is allied with Russia and has provided Moscow with logistical support in the invasion of Ukraine.

Sabalenka argued that Belarusian and Russian athletes opposed the war.

"Nobody in this world, Russian athletes or Belarusian athletes, supports the war. Nobody," the Belarusian athlete said in Paris. "If we could stop it, we would do it."

Kostyuk criticized Sabalenka's stance, arguing that she did not explicitly condemn the war.

"She never says that she personally doesn't support this war, and I feel like journalists should change the questions that you ask these athletes because the war is already there," she said.

"I feel like you should ask these players who would they want to win the war because if you ask this question, I'm not so sure these people will say that they want Ukraine to win."

Sabalenka said that she understood why Kostyuk would not want to shake hands with Russian and Ukrainian players, adding that she did not believe the athlete deserved to be booed over the gesture.

Last year, Kostyuk refused to shake hands with Belarusian player Victoria Azarenka at the US Open.

A number of sports tournaments, including the French Open, have allowed the athletes to participate as neutral players without national flags. Kyiv and many Ukrainian players have voiced opposition to this development.

Putin orders tougher Russian border security

Russian President Vladimir Putin on Sunday mandated tougher border security to facilitate "fast" Russian military and civilian movement into Ukrainian areas now controlled by Russia and "reliably cover" the lines near the combat zone.

Putin addressed the border service on their Border Guard Day holiday.

"It is necessary to ensure the fast movement of both military and civilian vehicles and cargo, including food, humanitarian aid building materials sent to the new subjects of the (Russian) Federation," Putin said in a message posted on the Kremlin's Telegram messaging channel.

Putin announced last September the annexation of the Ukrainian regions of Kherson, Zaporizhzhia, Luhansk and Donetsk, in a move widely condemned as illegal by Kyiv and its Western allies. 

Zelenskyy orders more sanctions against Russia 

Ukrainian President Volodymyr Zelenskyy unveiled new sanctions targeting Russia-affiliated businesses and entities.

Zelenskyy announced adding more companies and individuals to a list of those "who work for terror," vowing tougher measures against Russia.

The Ukrainian president dubbed Saturday as "another sanctions day" during his daily evening address. Two hundred and twenty companies and 51 people were added to the list. Zelenskyy said most were arms companies linked to Russian businesses, though not all those listed were operating on Russian soil. 

The Ukrainian president also thanked allies Germany, Finland, Canada and Iceland for fresh weapons deliveries, as well as Japan, which issued earlier this week a new package of sanctions against Russia.

Lavrov: 'West playing with fire' over F-16 promise

Russia's top diplomat has warned Western nations against providing Ukraine with US-made F-16 fighter jets, calling it "an unacceptable escalation" of the conflict.

"It's playing with fire, without a doubt," Foreign Minister Sergei Lavrov said in an excerpt from a Russian TV interview posted on social media.

Lavrov denounced the move as an attempt to "weaken Russia" by "Washington, London and their satellites in the EU."

South Africa to probe mysterious Russian ship activity

South African President Cyril Ramaphosa has appointed a panel to investigate US allegations that a Russian ship had collected weapons from a naval base near Cape Town last year.

"The President decided to establish the inquiry because of the seriousness of the allegations, the extent of public interest and the impact of this matter on  South Africa's international relations," said a statement from the presidency.

The probe will try to establish who was aware of the cargo ship's arrival, the contents that were loaded and off-loaded and "whether constitutional, legal or other obligations were complied with," the statement added.

The investigation is expected to take six weeks.

US ambassador Reuben Brigety said on May 11 that he was confident that a Russian ship, which docked at a naval base in Simonstown in the Western Cape in December last year, took aboard weapons from South Africa.

The South African government has denied the allegation.

The allegations have caused a diplomatic row and called into question South Africa's non-aligned position on the Ukraine conflict.

South Africa says it is impartial and has abstained from voting on UN resolutions on the war.

Prigozhin: Russian media banned from reporting about me

Yevgeny Prigozhin, the founder of the Wagner mercenary group, warned of a backlash from the Russian people if the country's media continued to avoid reporting on him.

Prigohzin said in an audio interview that he is "absolutely convinced" Russian media have been "forbidden" from covering his role in the conflict.

Despite Kyiv's denials, Wagner's forces claimed last weekend to have captured the Ukrainian city of Bakhmut after a monthslong war of attrition.

But Prigohzin role in the victory was played down on state television and his victory speech was not aired.

The Kremlin, meanwhile, released a 36-word statement congratulating Wagner and armed forces units for "liberating" Artyomovsk, the Soviet-era name for Bakhmut used by Russia, but it did not name Prigozhin.

"That high-level bureaucrats, those very towers of the Kremlin, are trying to shut the mouths of everyone so that they don't speak about Wagner will only give another shove to the people," the Wagner chief said.

"In the long term — long term is two or three months — they will receive a finger-slap from the people for trying to shut everyone's mouths and ears," he added.

Prigozhin has been fiercely critical of some of the Russian officials behind the Ukraine conflict, using obscene language and prison slang to insult Putin's top military brass including Defence Minister Sergei Shoigu.

Prigozhin's outbursts appear to break the rules of the tightly controlled political system crafted by Putin.

mm, rmt/wd (AFP, AP, dpa, Reuters)