Kyiv says the Ukrainian and Russian presidents have agreed that the cease-fire in eastern Ukraine is largely holding, despite reports of scattered skirmishes and a Red Cross mission called off because of "shelling."
The office of Ukrainian President Petro Poroshenko said on September 6 that he and Vladimir Putin discussed ways to ensure the truce, which took effect on September 5, becomes durable.
Poroshenko has said it was important now to start working on a long-term solution to the conflict, which has killed 2,600 people since April.
The statement said the two leaders stressed the need for the "maximum involvement" of the Organization for Security and Cooperation in Europe (OSCE) in monitoring the situation and for cooperation in providing Ukrainian and international humanitarian help.
The separatists have said the cease-fire agreement does not change their policy of wanting to break away from Ukraine.
Western states that accuse Russia of supporting the separatists with troops and weapons have been skeptical of the deal.
There were some reports from pro-Kyiv sources of attacks on Donetsk airport -- which is held by Ukrainian forces -- and a handful of other areas overnight. One unconfirmed report from the all-volunteer, pro-Kyiv Aidar battalion said 11 of its fighters had been killed in an ambush early on September 6.
Moreover, the International Committee of the Red Cross said via Twitter that it had abandoned a humanitarian mission to Luhansk earlier on September 6 due to "shelling."
Russia, which annexed Crimea in March in a move condemned by many countries and recognized by almost none, denies any direct involvement in the conflict.
Even as the cease-fire began, EU ambassadors on September 5 agreed new, tougher sanctions against Russia.
The measures are to be formally adopted on September 8. But diplomats said they could be suspended if the cease-fire held and if Russia withdrew forces from Ukraine.
The 12-point agreement was signed at talks involving representatives of Ukraine and the separatists, alongside envoys from Russia and the OSCE in the Belarusian capital, Minsk.
It came after the rebels' recent gains in their counteroffensive against government troops, which the West says were achieved with the support of several thousand Russian soldiers.
Some Russian nongovernmental groups claim at least 10,000-15,000 Russian troops have served in Ukraine since the pitched fighting broke out in early April.
Russia denies sending soldiers across the border, and President Vladimir Putin earlier this week unveiled a cease-fire blueprint.
Reports say that under the cease-fire agreement, both sides should start pulling back their units from major flashpoints and exchanging prisoners on September 6.
Russia would also be allowed to send a humanitarian aid convoy to the region.
Ukrainian Prime Minister Arseniy Yatsenyuk said the agreement required US and EU backing because Kyiv could "not manage with Russia on our own."
Diplomats said the fresh EU sanctions include an expanded list of individuals under an EU travel ban and asset freeze, restrictions on Russian state-owned companies borrowing on EU markets, and a ban on sales of goods with dual military and civilian use.
U.S. President Barack Obama said the cease-fire had been agreed because of US and EU sanctions against Russia.
NATO, at a summit in Britain on September 5, approved a rapid-response force of several thousands soldiers that could be deployed quickly to the alliance's eastern borders, acknowledging the perceived threat from Russia.