The agreement, reached after seven hours of negotiations in Geneva, requires all sides to refrain from “violence, intimidation or provocative actions”.
Thrashed out by representatives of the United States, European Union, Russia and Ukraine, it was finalised after confirmation that three pro-Russian protesters had been killed and another 13 injured in clashes with Ukrainian forces.
The deal calls for the disarming of all illegally armed groups and for control of buildings seized by pro-Russian separatists during the protests to be turned back over to Ukrainian authorities.
It also gives an amnesty to protesters who comply with the demands, except those found guilty of committing capital crimes.
Monitors from the Organisation of Security and Co-operation in Europe will be tasked with helping Ukrainian authorities and local communities comply with the agreement.
There will also be scrutiny of Kiev’s plans to reform its constitution and transfer more power from central government to regional authorities. The deal says this must be inclusive, transparent and accountable – including through the creation of a broad national dialogue.
The tentative agreement could put on hold – for now at least – economic sanctions the West had been prepared to impose on Russia if the talks were fruitless. That would ease international pressure, both on Moscow and nervous EU nations that depend on Russia for their energy.
United States secretary of state John Kerry called the deal the result of a “good day’s work” but emphasised that the words on paper must be followed by concrete actions.
He said he had warned Russian foreign minister Sergey Lavrov that Moscow would soon feel the sting of new sanctions should it not follow through on its commitments.
“It is important that these words are translated immediately into actions,” Mr Kerry said at a news briefing. “None of us leaves here with a sense that the job is done because of words on a paper.”
He added if Moscow did not abide by the agreement, “then we will have no choice but to impose further costs on Russia”.
EU foreign policy chief Baroness Catherine Ashton said the agreement contained “concrete steps that can be implemented immediately”.
Andrii Deshchytsia, Ukraine’s foreign minister, said the “joint efforts to launch the de-escalation will be a test for Russia to show that it is really willing to have stability in this region”.
Ukraine had been hoping to use the Geneva talks to head off Russian “aggression” and calm hostilities with its neighbour.
The agreement followed a day of escalation, in which three pro-Russian protesters were killed during clashes with Ukrainian troops, with another 13 injured.
The violence erupted during an attempted raid on a Ukrainian national guard base in the Black Sea port of Mariupol.
It was the most violent sequence of events during the confrontation that has pitted Ukraine’s new government in Kiev against a pro-Russian insurgency in its eastern regions, which is being tacitly supported by Moscow.
According to the Ukrainian authorities, the bloodshed occurred when a mob of about 300 people armed with guns, stun grenades and firebombs descended on the base.
Wearing masks and carrying modern firearms, their sophisticated equipment fuelled suspicions that much of the unrest is being stirred with Russia’s backing.
Ukraine’s interior ministry said shots fired by servicemen in the Mariupol base had initially proved insufficient to deter the pro-Russian crowd from proceeding with their assault. There were no casualties among Ukrainian servicemen. At least 63 people involved in the attack were detained, but local media quoted police as saying 38 of them were later released.
The southern Ukrainian city lies on the road running from Russia along the coast to Crimea, the peninsula that Russia annexed last month.
Nato says Russia has up to 40,000 troops along its border with Ukraine. If Russia was eyeing a possible “land bridge” from Russia to Crimea, it would need to take over the region that includes Mariupol.
Speaking in parliament, acting Ukrainian president Oleksandr Turchynov said a pro-Russian gang carrying automatic weapons had attempted to storm the base three times.
Footage filmed outside the base on Wednesday night showed an unidentified man going out to speak to masked men in the crowd armed with assault rifles. The masked men insisted they wanted no bloodshed.
A short while later, however, a crowd of mainly masked young men armed with bats and sticks began throwing Molotov cocktails at the base’s gate and trucks parked in front of it.
One soldier involved in the battle, a 20-year-old conscript who gave his name only as Stanislav, said troops had been forced to act in self-defence.
“We were attacked by unidentified people and we didn’t want to shoot, but they were behaving aggressively,” he said.
Earlier, in a marathon four-hour televised question-and-answer session, president Vladimir Putin took the opportunity to dismiss as “nonsense” claims that Russian special forces had been fomenting the unrest in eastern Ukraine.
“It’s all nonsense, there are no Russian units, special forces or instructors, in the east of Ukraine,” he said.
However, he did admit – for the first time – that troops in unmarked uniforms who had captured Ukraine’s Crimean peninsula, before its annexation last month by Moscow, were Russian soldiers.
Tim Ripley: Talks freeze current stalemate but leave little hope of Kiev being able to exercise power
Yesterday’s talks in Geneva appeared to signal the end of the Ukraine crisis, with all sides at the four-party talks agreeing to begin de-escalating violence and tension. But there was little sign of the Ukrainian delegation after the talks, perhaps signalling that they were less enthusiastic about the “outbreak of peace and harmony”.
From Kiev’s perspective, last night’s deal raises fears that the country could soon be dismembered by stealth and supporters of the old regime allowed to return to government. Talk of non-violence is good news for the United States and European Union because it avoids them having to implement trade sanctions against Russia that might seriously damage their own economies.
However, it also freezes in place the current stalemate in eastern Ukraine and potentially prevents Kiev acting against the separatist administrations that have sprung up.
The People’s Republic of Donetsk – set up by pro-Russian separatists – is still in place and it remains committed to holding a Crimea-style referendum on joining Russia on 11 May.
Police across the east of Ukraine have gone over to the separatists and without the threat of force, it remains highly unlikely that Kiev will be able to exercise any power in the region even if the “little green men” of Russian intelligence melt away into the background. They have already achieved their aims of breaking the Russian-speaking east away from Kiev’s control. While America’s and Europe’s top diplomats talked of inclusion, constitutional mechanisms and other niceties, in Ukraine the pro-democracy regime set up in Kiev after the fall of former president Viktor Yanukovich seems to be fatally weakened.
Democratic elections set for 25 May look like being eclipsed by the Moscow-inspired independence referendum in the east. The vision of a democratic Ukraine, governed by the rule of law and linked to Europe that was at the heart of the February revolution in Kiev, looks like an illusion.
A messy compromise with Kremlin and oligarch power is now the only way to avoid Putin’s “little green men” rolling westwards.