MOSCOW—Russia urged Kiev on Tuesday to open talks quickly with rebels on what will become of areas held by separatists in eastern Ukraine, a crucial issue that remains unresolved days after a cease-fire took hold.

Russian President Vladimir Putin and his Ukrainian counterpart Petro Poroshenko discussed the cease-fire Tuesday as well as economic issues in their second phone call in two days.

The Kremlin said Mr. Putin "confirmed the Russian Federation's readiness to continue to promote a peaceful resolution of the crisis." Mr. Poroshenko's office confirmed the call and said they discussed a range of questions connected with the cease-fire. Neither side elaborated.

Earlier in the day, Russian Foreign Minister Sergei Lavrov called for talks to begin soon on the question of how much autonomy rebel-held areas in the Donetsk and Luhansk regions of eastern Ukraine, along the Russian border, will gain under the peace plan.

Both the Ukrainian government and the separatists said the cease-fire was generally holding despite mutual accusations of scattered violations. Mr. Lavrov also said the cease-fire was holding "in general."