Ukraine in maps: How the crisis spread
The crisis in Ukraine began in November last year when pro-Moscow President Viktor Yanukovych abandoned a deal with the EU in favour of stronger ties with Russia.
Protests erupted in the capital Kiev and quickly escalated as government buildings were seized in cities across the western regions of Ukraine.Protests in western Ukraine, January 2014
On 20 February at least 88 people were killed in 48 hours in Kiev.
Videos showed uniformed snipers firing at protesters holding makeshift shields. President Yanukovych signed a ceasefire deal with the opposition but then disappeared and parliament voted to remove him from power.
Ukraine has been torn between east and west since the collapse of the Soviet Union in 1991. While Ukrainian is the main language in western regions, Russian is predominant in parts of the east and south.
The division is also reflected in voting patterns. Mr Yanukovych received most support in the southern and eastern regions of Ukraine in the 2010 election.Protests spread south to Crimea
On 27-28 February pro-Russian gunmen seized key buildings in the Crimean capital, Simferopol.
Within days parliament voted to join Russia and called a referendum.
Russia later admitted that its military had helped the Crimea insurgents.
The majority of Crimea's 2.3 million population identify themselves as ethnic Russians and speak Russian - a legacy of Russia's 200-year involvement in the region.
Russia's Black Sea Fleet also has its historic base in the Crimean coastal city of Sevastopol.
On 16 March, 97% of voters reportedly backed the proposal to join Russia. That figure was later disputed, with leaked documents showing only 50-60% support for the move.
The EU and US condemned the annexation of Crimea and imposed a first round of sanctions on Russian officials and high-ranking Moscow allies in Ukraine.Trouble spreads east
Pro-Russian sentiment is strong in eastern regions such as Donetsk and Luhansk, Ukraine's industrial heartland. After the withdrawal of Ukrainian troops from Crimea, there were reports of large numbers of Russian troops gathering just over the border.
On 7 April protesters occupied government buildings in the eastern cities of Donetsk, Luhansk and Kharkiv.
Although Kharkiv was retaken the following day, the occupations spread to other cities, and a number of pro-Russian leaders declared that referendums on granting greater autonomy to eastern regions would be held.Towns targeted by separatists, April 2014 Eastern referendum
On 11 May pro-Russian separatists in Donetsk and Luhansk declared independence after the referendums, which were not recognised by Kiev or the West.
A build-up of Russian troops on the shared border in April sparked concern that another annexation could take place.Presidential election
Elections for a new president in Ukraine were held on 25 May resulting in confectionery tycoon Petro Poroshenko being elected with over 55% of the vote, although no polling stations were open in Donetsk city and several other locations.
On 20 June President Poroshenko announced a 15-point peace plan and declared a week-long truce. It held for a few days until a military helicopter was shot down over eastern Ukraine.
With a government offensive launched once more, on 5 July rebels abandoned strongholds in the north of Donetsk region, withdrawing to a smaller area of insurgency in the south.Malaysia Airlines tragedy, 17 July 2014
On 17 July Malaysia Airlines flight MH17 from Amsterdam was shot down near the village of Grabove in rebel-held territory close to the border with Russia.
Almost 300 people were killed in the crash - everybody aboard the airliner. Western nations blamed a Russian-supplied missile, believed to have been fired by rebels.
Russia denied it had armed the rebels and argued instead that a Ukrainian fighter jet had flown near the airliner at the time.
Ukraine insists Russian regular forces are involved in the fighting in Ukraine. It has also accused the Russian authorities of allowing well-trained volunteers and heavy weapons to cross the border to help the rebels. Russia dismissed those accusations, yet the rebel leader in Donetsk said many Russian soldiers had joined the rebel cause.New front
Ukrainian forces made gains in some areas previously held by the rebels. But on 27 August the rebels - allegedly backed by Russian heavy armour - opened up a new front on the coast, seizing the town of Novoazovsk and threatening the strategic port city of Mariupol.
Ukrainian and Russian officials opened talks with separatist leaders and international monitors in Minsk on 1 September. Russian Foreign Minister Sergei Lavrov said he wanted the talks to focus on "agreeing an immediate and unconditional ceasefire".
The first face-to-face talks between Russian President Vladimir Putin and Mr Poroshenko on 26 August failed to make progress.
Nato has announced it is assembling a "readiness force" in response to Russia's actions over Ukraine. Details are to be confirmed at a summit meeting in Wales, which starts on 4 September.
About 2,600 people have been killed in the fighting since mid-April (not including the passengers and crew involved in the MH17 plane crash), according to a UN report on 29 August.
Nearly 350,000 people have fled their homes - about 190,000 have gone to Russia.Ukraine's economic ties
The EU and US have imposed asset freezes and travel bans on many senior Russian officials and separatist leaders.
Further sanctions were announced on 29 July following the downing of Flight MH17.
The EU has now threatened more sanctions against Russia, unless it stops supporting the rebels.
Ukraine's trade volumes with the EU and Russia are quite similar.
It imports most of its gas and oil from Russia. About one-third of Europe's gas also comes from Russia - about half of it through Ukraine.
Ukraine is heavily in debt. A rescue package offered by Russia was cancelled after the protesters forced out Mr Yanukovych.
The International Monetary Fund has now approved a $17.1 bn (£10.1 bn) bailout for Ukraine. With funds from other donors, including the EU, the total package will be worth £32.1bn.
But the loan is dependent on strict economic reforms, including raising taxes and energy prices, which are unlikely to prove popular with voters.