Leaders of France, Germany and Russia have agreed with Ukraine on the dispatch of OSCE monitors to 10 flashpoint sites on the country's eastern frontline to shore up a shaky truce, Ukraine said Tuesday.

In a readout of a four-way telephone conversation published by the Ukrainian presidency, President Petro Poroshenko, German Chancellor Angela Merkel, French President Francois Hollande, and Russian President Vladimir Putin "supported Ukraine's suggestion to put monitors to all locations of ceasefire violations."

Ukrainian Foreign Minister Pavlo Klimkin on Tuesday cast doubt on hopes that a UN-backed truce with pro-Russian rebels will stick, as he called for an expansion of international monitoring.

"The situation on the ground is very difficult and tense despite a declared ceasefire. We still have many shells thrown by terrorists" in eastern Ukraine, Klimkin told reporters in Tokyo.

France will "not tolerate the slightest infringement" of the Minsk peace accord in Ukraine warned President Francois Hollande following a meeting with NATO chief Jens Stoltenberg in Paris Monday.

"The Minsk accord is the only possible basis to re-establish peace," Hollande told reporters.

Estonia's governing pro-NATO Reform party was set Monday for tricky coalition talks after defeating a Kremlin-oriented rival in an election held amid jitters over the actions of neighboring Russia.

President Toomas Hendrik Ilves is expected to task Reform leader and outgoing Prime Minister Taavi Roivas with forming a government after the centrist party won 30 seats in the 101-member parliament in Sunday's vote.

The EU said it hoped for a "positive outcome" in talks in Brussels on Monday between the Russian and Ukrainian energy ministers aimed at resolving a gas supply dispute threatening deliveries to Europe.

Russian state-owned gas giant Gazprom threatened last week to cut deliveries to Ukraine and divert supplies instead to eastern parts of the country controlled by pro-Kremlin rebels.

The U.S. and Russian foreign ministers expressed cautious optimism after holding talks in Geneva Monday to end fighting in Ukraine, where the U.N. says more than 6,000 people have died in less than a year.

The meeting between John Kerry and Sergei Lavrov in Geneva was just one of several attempts at mediation on the conflict Monday, as high-stakes talks to resolve a bitter gas dispute between Kiev and Moscow took place in Brussels.

U.N. rights leaders on Monday decried the "merciless devastation of civilian lives and infrastructure" in Ukraine as the death toll passed 6,000, warning that targeting civilian areas could be a "crime against humanity."

The United Nations' ninth report on the situation in violence-wracked Ukraine paints a bleak picture of developments in the country and warns there has been a "serious escalation" of the conflict since the beginning of the year.

A Ukrainian lawmaker said Sunday he was detained by Russian police ahead of a Moscow march to honor opposition leader Boris Nemtsov, who was gunned down near the Kremlin.

"Police have detained me," Alexei Goncharenko wrote on Facebook. "I did not shout anything, did not carry any banners or flags -- they simply detained me over the T-shirt."

A week since pro-Russian rebels forced Ukrainian soldiers from the key transport hub of Debaltseve, the sound of explosions still reverberates around the eastern town.

This, however, is not the boom of artillery fire and combat -- it is teams of Cossack deminers from the separatist side blowing up mines and unexploded ordnance littering this war-scarred railway junction.

Estonians voted Sunday in an election marked by jitters over a militarily resurgent Russia and a popular pro-Kremlin party, with the security conscious center-left coalition tipped for a return to power.

Moscow's annexation of Crimea last year and its meddling in eastern Ukraine have galvanized the European Union, including this eurozone member of 1.3 million people, a quarter of whom are ethnic Russian.