The leaders of France, Germany and Russia discussed the Ukraine crisis over the phone on Saturday and agreed to hold a new summit in the coming weeks, said the French presidency.

Francois Hollande, Angela Merkel and Vladimir Putin once again reaffirmed their support for the "Minsk II" peace measures agreed in February.

"They strongly supported the call for a complete ceasefire from September 1 at the time of schools reopening," said the Elysee palace in a statement.

They suggested that a new summit in the "Normandy Format" — the three leaders, plus those of Ukraine — "could be useful in the coming weeks," the statement added.

Ukrainian President Petro Poroshenko last week accused Russia of sending huge numbers of reinforcements to aid separatists in the east of the country.

During the phone call, Putin expressed his concern over the "continual bombardment of towns in the Donbass region by the Ukrainian army and the concentration of Ukrainian armed forces all along the demarcation line," the Kremlin said in a statement.

Putin also insisted on a direct dialogue between Kiev and separatist leaders in the east, as well as the removal of economic blockades on the region.