The Syrian Observatory for Human Rights reported Saturday that "Islamic State" (IS) militants had been attacking government positions 4 kilometers (2.5 miles) from Palmyra and entered the city after killing at least 49 pro-government soldiers.

The Observatory also reported that a government jet had crashed in the Jazal area while flying raids against IS near Palmyra.

IS' Aamaq news agency claimed its militants had downed the jet near the Jazal oil fields west of the city. The activist-run Palmyra Coordination Committee said the jet was a MiG-23.

Syrian government forces - backed by the Russian military - had recaptured Palmyra and its ancient Roman ruins from IS in March, and the two militaries then turned to fighting local opposition forces in Aleppo and Damascus.

IS destroyed many of the city's ancient monuments.

Kerry pleads with Moscow

US Secretary of State John Kerry and European and Arab diplomats have been meeting members of Syria's opposition in Paris, with Kerry saying he is working to save Aleppo "from being absolutely, completely destroyed."

The meeting ended with Kerry pleading with the regime, Russia and Iran to show "a little grace" and end the "indiscriminate" bombing of Aleppo, which looks set to fall into the hands of Assad's forces soon.

The Syrian government's push - preceded by months of airstrikes that destroyed rebel positions as well as schools, hospitals, and first responder centers - has destroyed swathes of the city's eastern neighborhoods, held by the opposition since 2012.

Rebels reportedly held their ground on Saturday after two weeks of advances by government forces and allied militias in the city.

Opposition activists accused the government of dropping bombs with chlorine gas on the Kalaseh neighborhood, one of the few still held by the opposition, in the early hours of Saturday.

De facto partition?

"The partition of Syria is happening," French Foreign Minister Jean-Marc Ayrault said after a meeting of diplomats in Paris on Saturday. "What sort of peace is it if it's only the peace of cemeteries?"

A European diplomat - speaking on condition of anonymity - told the French news agency AFP that there was a "de facto division of Syria."

"The Russians are to the west and the Western powers of the anti-jihadist coalition are to the east," he said.

Extremists from Fateh al-Sham, the former al Qaeda affiliate previously known as Al-Nusra Front, and the Islamic State group, as well as US-backed Kurdish militias in the north, retain control of many areas.

Civilians feeling

Russia's Defense Ministry, which is supporting Syrian government operations in Aleppo, said 50,000 civilians had fled eastern Aleppo over the past two days in a "constant stream." Ministry spokesman Maj. Gen. Igor Konashenkov said the Russian military was providing civilians who have left eastern Aleppo with temporary accommodation, hot meals and medical assistance.

Over 400,000 displaced people are reportedly now in west Aleppo. 

The Syrian Observatory for Human Rights said "hundreds" had fled in recent days, but that over 80,000 had been displaced over the past two weeks. The UN estimated that over 30,000 people fled.

What after Aleppo?

Once the city falls, the largest remaining rebel bastion will be Idlib province, controlled by a coalition dominated by extremists from a former al Qaeda affiliate. IS remains in control of territory around its de facto capital, Raqqa.

The US defense secretary said on Saturday that 200 more military personnel will be sent to Syria to strengthen the fight against IS in Raqqa.

jbh/sms (AP, AFP, dpa)