and for the terms of a lasting ceasefire, warning Moscow they were ready to impose further sanctions.
During their summit in Brussels, EU leaders said in a statement on Friday that they also expected Ukrainian authorities should be granted control of three main border checkpoints.
In talks with French President Francois Hollande and German Chancellor Angela Merkel at the summit, Ukrainian President Petro Poroshenko said he had proposed extending the current, temporary ceasefire for 72 hours from Friday's expiry at 1900 GMT.
The ceasefire between the rebels and the government, set to expire later on Friday, has already been marred by a number of violations, including the downing of a Ukrainian helicopter earlier this week with the loss of all nine people on board.
Earlier, rebels in southeast Ukraine released four out of eight international observers, captured over a month ago, in an apparent goodwill gesture that could help pave the way to a resolution of the conflict that has so far claimed hundreds of lives.
Pro-Russian separatists had detained eight observers from the Vienna-based Organization for the Security and Cooperation in Europe (OSCE), a key security and rights body, tasked with monitoring an agreement drafted in Switzerland in April to de-escalate the crisis that has pitted the rebels against leaders in Kiev.
Four observers from Switzerland, Turkey, Estonia and Denmark, part of the 100-strong mission, were brought by heavily armed rebels to a hotel in downtown Donetsk, where they were handed over to their colleagues.
Securing the release of the four OSCE hostages has been a part of peace consultations between mediators of the Kiev government, OSCE, Russia and rebel leaders.
On another note, the UN refugee agency said that some 16,400 people fled their homes in eastern Ukraine in the past week, many citing a deteriorating situation and fears of abduction, bringing the number of displaced within the country to 54,000.
"We are seeing a sharp rise in internal displacement in Ukraine," Melissa Fleming, chief spokeswoman of the UN High Commissioner for Refugees (UNHCR), told a news briefing.
Another 110,000 people have left Ukraine for Russia so far this year, only 9,500 of whom have sought refugee status, while 700 others have gone to Poland, Belarus, the Czech Republic and Romania, she said.
REUTERS