Donetsk, Ukraine (CNN) — Long lines of cars jammed the roads leading south out of Donetsk in eastern Ukraine Saturday, as residents attempted to flee the city center after a night of heavy shelling on the city’s northern outskirts.

Hundreds of vehicles were caught in heavy traffic, and trains are no longer running in and out of the city, which is a stronghold for the pro-Russia rebels.

There was heavy shelling and antiaircraft fire on the outskirts of the city to the north throughout the night. There has been sustained fighting in the area for weeks, but it appeared more intense overnight than in recent days.

Russian news agency Interfax reported a dramatic increase in the number of Ukrainian refugees seeking refuge over the border in Russia.

“The Ukrainian government officials were seeking to encircle the city, really squeeze the remaining pro-Russian separatist forces that had fallen back there since being driven out of other strongholds across Eastern Ukraine,” said CNN’s Phil Black, reporting from a congested road in Donetsk while scores of people attempted to leave.

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