European leaders remain sceptical about Russia's part in a ceasefire agreement reached at Minsk and have warned that Moscow would face further sanctions if violence continues in eastern Ukraine.

German Chancellor Angela Merkel told a press conference in Brussels: "If there are difficulties, then we would not rule out further sanctions. Actions must now follow words ... Therefore we are keeping every option to react open."

The ceasefire is to begin in eastern Ukraine after midnight (22:00 GMT) on Saturday.

Besides Merkel, French President Francois Hollande, Russian President Vladimir Putin and Ukraine's President Petro Poroshenko were part of marathon talks that culminated in the ceasefire deal. A consensus was reached about pulling back heavy weapons and prisoner exchanges, though other major issues persist.

President Hollande said: "We would get back into the procedure that you know ... where sanctions would be added to the sanctions that are already in place."

The EU currently has a deadline of 16 February to decide whether or not to extend the visa bans and asset freezes on 19 people including Russians and anti-Kiev rebels. The EU has already blacklisted more than 100 pro-Russian individuals and 28 entities in various sectors including energy and finance over the Ukraine conflict.

"Our trust in the goodwill of President [Vladimir] Putin is limited. It is why we have to maintain our decision about sanctions. We didn't discuss any new sanctions but we didn't decide also about postponing the sanctions," said President of the European Council, Donald Tusk.

Meanwhile, the BBC reports there has been more shelling in the rebel-held cities of Donetsk and Luhansk, a day after the Minsk agreement.

There are no confirmed reports of casualties. Both cities are near the front line where the pro-Russian rebels face government forces.

BBC journalists in Donetsk heard new shelling on Friday morning, though they said it sounded less intense than in recent days.

Luhansk also came under bombardment overnight.