MOSCOW Russian Foreign Minister Sergei Lavrov sought to fend off fresh accusations from Kiev that Moscow is sending soldiers and weapons to Ukraine and said he hoped for progress at talks on the conflict on Wednesday despite renewed fighting.
Kiev accused Russian regular forces on Tuesday of attacking its troops in eastern Ukraine, one of its boldest assertions yet that Russia's military is directly involved in a conflict in which more than 4,800 people have died since last April.
Ukrainian President Petro Poroshenko told the World Economic Forum in Davos, Switzerland, on Wednesday that Russia had 9,000 troops in Ukraine and demanded their withdrawal.
"I say every time: if you allege this so confidently, present the facts. But nobody can present the facts, or doesn't want to," Lavrov told a news conference before heading to peace talks in Berlin with the foreign ministers of Ukraine, Germany and France.
"So before demanding from us that we stop doing something, please present proof that we have done it."
However, Lavrov acknowledged that the pro-Russian separatists in eastern Ukraine were holding more territory than assigned to them under a ceasefire agreement reached last September in Minsk, capital of Belarus.
Fighting in eastern Ukraine increased sharply this month, leaving the ceasefire in tatters. The leaders of Germany and France have refused to meet Russia's President Vladimir Putin to discuss the crisis until Moscow ensures progress on the truce.
Lavrov said Russia had received assurances from the separatists that they would retreat to the separation lines agreed last September. He did not say when this might happen.
Kiev says rebels have seized more than 500 square km (194 square miles) of land beyond the agreed lines.
German Chancellor Angela Merkel said on Wednesday she hoped the four-way talks in Berlin could help implement the elusive ceasefire but warned against expecting too much.
Lavrov said he hoped the talks would lead to a summit of the four countries' leaders.
Russia has said the talks should put pressure on Kiev to engage in direct talks with the separatists and push through constitutional reforms giving eastern Ukraine more autonomy.
Lavrov said Moscow believes the largely Russian-speaking eastern regions should remain within Ukraine.
"We hope the contacts to be held in the foreseeable future at various levels and in various formats will help move ahead in this direction," he added.
(Reporting by Gabriela Baczynska, Additional reporting by Lidia Kelly and Thomas Grove, Writing by Gabriela Baczynska, Editing by Timothy Heritage and Gareth Jones)