In a telephone call with Russian President Vladimir Putin, French President Francois Hollande and German Chancellor Angela Merkel said they were "extremely worried" about the ongoing fighting in Ukraine.
Their remarks come after pro-Russian separatists shot down a Ukrainian military plane on Saturday, killing all 49 people on board. The attack is the deadliest in more than two months of clashes between pro-Kremlin rebels and Ukrainian army forces in the country's east.
Both Hollande and Merkel stressed the importance of reaching a rapid ceasefire to stop further unrest.
In a statement, they called on Putin to exert his influence over pro-Russia separatists to stop the transfer of more fighters and weapons across the border. Moscow has regularly been accused by the West of supplying the rebels with heavy weaponry.
On Sunday, Ukrainian President Petro Poroshenko met with his defense and security chiefs to discuss how to deal with the pro-Russian separatists responsible for the downing of the plane.
"All those involved in cynical acts of terrorism of this magnitude must be punished," Poroshenko said in a press release. "
The attack took place hours before crucial gas talks bewteen Moscow and Kiev to settle a multi-billion dollar energy bill.
If no agreement is reached before Monday, Moscow will cut off Ukrainian gas supplies. Hollande and Merkel have called on both sides to strike a deal.