New shelling in rebel-held eastern Ukraine has killed at least one person, a day after Russia and European leaders agreed on a ceasefire deal aimed at ending the 10-month war.

The continuing fighting between government forces and pro-Russian rebels occurred early on Friday in the cities of Donetsk and Luhansk, local residents reported.

On Thursday, European powers warned Russia it risked fresh sanctions if the ceasefire deal was not implemented.

The agreement to end the nearly year-long conflict, which has killed thousands, was reached earlier on Thursday after marathon talks in the Belarusian capital Minsk between the leaders of Russia, Ukraine, France and Germany.

Kiev and the West accuse Russia of stoking the war in ex-Soviet Ukraine by pouring arms and troops to help the pro-Russian rebels fighting government troops in the country's industrial east.

Moscow denies the charges.

Speaking after a European Union summit in Brussels, German Chancellor Angela Merkel warned Russia that the bloc, which has already slapped Moscow with sanctions over the crisis, was not ruling out further measures if the truce failed.

"If it works well we would be very happy to go with the agreement. If there are difficulties we wouldn't rule out other sanctions," she said.

French President Francois Hollande, who along with Merkel attended the 17-hour talks in Minsk that also included Russian President Vladimir Putin and Ukrainian President Petro Poroshenko, agreed.

If the ceasefire deal was not respected, "we would return to a process ... of sanctions that would be in addition to those already in place".

Hollande also said that the conditions were not yet right for France to resume with the delivery of two Mistral warships to Russia, a 1.2-billion-euro sale that Paris was forced to suspend over the Ukraine crisis.

Under the deal reached in Minsk, a ceasefire is to take effect at midnight Kiev time on Sunday (22:00 GMT on Saturday) and heavy weapons are to be withdrawn from the frontlines of the conflict, which has killed at least 5,300 people and driven a million people from their homes since erupting in April 2014.

Poroshenko described the 17-hour talks as "very difficult" and said he expected the implementation of the deal would not be easy.

Escalating violence

The United States, which has said it could supply Ukraine with weapons if the conflict continues, cautiously welcomed the peace accord, but emphasised the work that still needs to be done in making it stick.

"The true test of today's accord will be in its full and unambiguous implementation," the White House said, including "restoration of Ukrainian control over its border with Russia".

The Ukrainian government accused Russia of deploying another 50 tanks across the border during the talks in Minsk, with fighting expected to continue around disputed railway hub Debaltseve, which rebels claim to have surrounded.

The roadmap was signed by Russian and Ukrainian envoys, separatist leaders and European mediators from the Organisation for Security and Co-operation in Europe.

A previous truce signed in Minsk last September quickly collapsed.