Russia's invasion of Ukraine sparked a host of anti-war demonstrations in cities around the world on Saturday.

Thousands of people gathered in London, Sydney, Geneva, Frankfurt, Berlin, Athens, Helsinki and other cities, with many demonstrators carrying the Ukrainian colors and banners denouncing Russia's invasion.

'Everybody is scared'

Many of those attending rallies have been calling for their governments to take tougher action against Russia, while expressing support for the people of Ukraine. The demonstrations follow similar protests seen around the world, including in Russia, since Moscow launched its invasion of Ukraine on Thursday.

In Switzerland, organizers said around 20,000 people flooded the streets of the capital of Bern.

In Geneva, hundreds gathered outside the headquarters of the United Nations with posters reading: "Say no to Putin."

In London, hundreds marched on the Russian embassy and smeared fake blood at the front of the embassy.

"You look at the people gathered here and everybody is scared... We had peace for 80 years and all of a sudden, war is back in Europe," said a protester among a gathering of around 2,500 in Munich's Karlsplatz square.

There were thousands of people in the German city of Frankfurt on Saturday with a rally organized by the co-ruling Green Party under the slogan, "Solidarity with Ukraine — Peace in Eastern Europe."

There have also been protests in India, where anger has been directed at NATO and Western powers.

"The kind of aggression we are witnessing in Ukraine has been forced by the US through NATO and also the Russian military forces who have entered Ukraine. Both are responsible for this situation," said a student activist at a protest in New Delhi.

Ukraine's President Volodymyr Zelenskyy tweeted about a large protest in Estonia, saying: "The largest demonstration in the modern history of Estonia took place in support of Ukraine. I am grateful to the Estonian people for their solidarity in these difficult times." 

Russia's voices of dissent

There have also been growing calls within Russia to bring a halt to the ongoing invasion.

A petition signed by hundreds of Russian medical professionals stated opposition to the actions in Ukraine.

"We, Russian doctors, nurses and paramedics, are decidedly against the attacks conducted by Russian troops on Ukrainian territory," the petition with more than 300 signatures stated.

Humanitarian groups have also spoken out, writing an open letter to Russian President Vladimir Putin, calling on him to bring an end to the fighting, saying: "War is a humanitarian catastrophe that leads to pain and suffering... We consider violent solutions to political conflicts inhumane and call upon you to cease fire and begin negotiations."

Russian authorities have clamped down on dissent and have arrested more than 2,000 people at demonstrations staged in the days following the invasion.

kb/mm (AP, dpa, Reuters)