French President Francois Hollande, German Chancellor Angela Merkel, and Ukrainian President Petro Poroshenko have called for "an immediate cease-fire" in eastern Ukraine, a day after the latest peace talks collapsed.
Speaking by phone to discuss a surge in deadly fighting between Ukrainian troops and pro-Russian rebels on February 1, the three leaders also expressed their regret for "the failure of the talks" in Minsk, the French presidency said.
Fighting has been particularly intense in recent days in and around the government-controlled town of Debaltseve, where rebels are trying to encircle Ukrainian troops.
The Ukrainian military said on February 1 that 13 of its soldiers had been killed and 20 wounded in Debaltseve and elsewhere in the war-torn east in the past 24 hours.
At least 17 civilians also died in fighting across the region, government officials and separatist rebels said.
Several people, including children, were injured when a Grad rocket launched by pro-Russian separatists hit a government building in Debaltseve, the Ukrainian military said.
The attack occurred when civilians were boarding a bus next to the government headquarters, trying to flee the city, the military said.
The fight for Debaltseve -- which has been without power, water, and gas for some 10 days -- has led hundreds of people to flee the area.
Minsk Talks Fail
The latest peace talks in Minsk, which lasted for more than four hours on January 31, included representatives from Russia, Ukraine, the Organization for Security and Cooperation in Europe (OSCE), and the self-proclaimed Donetsk and Luhansk people's republics.
The Foreign Ministry of Serbia, which chairs the OSCE, said the two separatist envoys blocked the negotiations and sought to revise a previous cease-fire deal.
In a statement issued on February 1, the ministry said, "They were not even prepared to discuss implementation of a cease-fire and withdrawal of heavy weapons."
Rebel representative Denis Pushilin said the separatists will reject ultimatums and accused Ukraine of blocking the peace process.
Kyiv's representative at the talks, former President Leonid Kuchma, said the two separatist representatives at the talks issued ultimatums and refused to discuss a plan "for a quick cease-fire and a pullback of heavy weapons."
Kuchma also criticized the two main, self-proclaimed separatist leaders in eastern Ukraine -- Aleksandr Zakharchenko and Igor Plotnitsky -- for not attending the talks as signatories of the original cease-fire agreement signed in Minsk on September 5.
Pushilin said before the talks began that Zakharchenko and Plotnitsky were "fully occupied" dealing with the consequences of the Ukrainian bombardments.
Pushilin repeated after the talks that the two main separatist leaders would attend peace talks only after Ukrainian President Petro Poroshenko declared an immediate cease-fire and pulled back heavy weaponry and their presence is needed to sign "the final document."
Pushilin added that Kuchma was not currently authorized to sign a final document on behalf of Ukraine.
Fighting Rages On
OSCE officials said before the talks that they hoped for a "binding" truce that would allow an "unrestricted supply of basic goods" as well as humanitarian aid to go to the civilians who are most affected by the fighting.
The peace talks in the Belarusian capital were being looked on as a chance to reduce the increased hostilities between separatist fighters and Ukrainian troops.
A total of more than 5,100 people have been killed and hundreds of thousands have fled their homes since the fighting began in April.
Ukrainian officials want separatist forces to pull back to the line of contact as outlined in the Minsk agreement, but the rebels are balking at that request as they have gained more than 500 square kilometers of Ukrainian territory since September and sit just outside the important seaport of Mariupol.
In a joint statement, rebel leaders from Donetsk and Luhansk said before the Minsk talks that if they failed their offensive would continue.
The latest violence has alarmed Ukraine's Western allies, with U.S. Secretary of State John Kerry announcing plans to visit Kyiv on February 5 for talks with Poroshenko and Yatsenyuk.
The State Department said Kerry will then meet with Russian Foreign Minister Sergei Lavrov on the sidelines of the Munich security conference.
Western governments and Ukraine accuse Russia of arming and training the rebels, who are deploying sophisticated and heavy weaponry, including dozens of tanks and multiple-rocket launchers.
Russia denies aiding the rebels.