French President Francois Hollande said Thursday the conditions were "still not right" to go ahead with the sale of two Mistral warships to Russia despite Moscow having backed a new Ukraine peace plan.

Hollande suspended the 1.2 billion euros ($1.5 billion) sale last year as the Ukraine crisis deepened, fearing it would boost Russia's military capabilities and put Paris in hot water with its allies.

The Ukraine ceasefire deal agreed Thursday appears little more than a sticking plaster that will allow Kiev and Ukraine rebels to wind down the fighting but leaves thorny questions on resolving the conflict unanswered, analysts said.

Some 16 hours of talks in the Belarussian capital Minsk -- which saw one reporter collapse with high blood pressure as negotiations continued through Wednesday night -- produced an agreement on a ceasefire to take effect from Sunday and the withdrawal of troops.

A new roadmap aimed at ending a 10-month war between Ukraine and pro-Moscow rebels was agreed in Belarus Thursday, but skepticism remained as leaders warned much needed to be done before peace was achieved.

After a marathon summit in the Belarussian capital Minsk, Russian President Vladimir Putin said he, Germany Chancellor Angela Merkel, French President Francois Hollande and Ukrainian President Petro Poroshenko had reached a ceasefire deal.

The leaders of Ukraine, Russia, Germany and France on Wednesday began a crunch peace summit in Minsk aimed at ending 10 months of fighting in Ukraine where violence claimed dozens more lives. 

A grave-looking Ukrainian President Petro Poroshenko shook hands briefly with Russian leader Vladimir Putin as the two arch-foes came face-to-face for the first time since October to try to thrash out a peace plan.   

Russia's alleged tactics in the Ukraine conflict including covert military action and social media campaigns could inspire other nations such as China and Iran, a top defense think-tank warned Wednesday.

Most armies around the world are ill-prepared to tackle this new type of "hybrid warfare", the International Institute for Strategic Studies (IISS) said in its annual Military Balance report.

Croatian nationals, believed to be mostly veterans of the country's 1990s war, joined Ukraine's army to fight against pro-Russian rebels, Foreign Minister Vesna Pusic said Wednesday without giving any numbers.

"As far as I know there are (Croatian fighters) who joined the Ukrainian army," Pusic told reporters and added that the country's intelligence services were "following the issue."

EU foreign affairs head Federica Mogherini told AFP on Wednesday that a high-stakes Ukraine peace summit in Minsk would be a turning point in the conflict.

Mogherini also urged Moscow to take the chance to become a "responsible actor" and help end the 10-month war between Kiev and pro-Russian separatists.

Prime Minister Tammam Salam has said that he received French assurances that Paris is continuing to exert efforts to end Lebanon’s presidential deadlock.

He told As Safir daily on Wednesday that he held around 14 meetings with Arab and Western officials in Germany last week “to prove Lebanon's presence on the international scene and shed light on the problems that it is suffering from.”

U.S. President Barack Obama called his Russian counterpart Vladimir Putin to discuss escalating violence in eastern Ukraine and "Russia's ongoing support for the separatists there," the White House said Tuesday.

During the call Obama reiterated America's support for Ukraine's "sovereignty and territorial integrity," National Security Council officials said.

Intense fighting in Ukraine, including a devastating rocket strike on Kiev's military headquarters in the east, killed at least 37 people on Tuesday on the eve of a four-way peace summit.

As diplomats scrambled to finalize a deal to end the 10-month war, pro-Russia rebels sought to encircle railway hub Debaltseve and Ukrainian forces launched a counter-offensive around the strategic port of Mariupol.