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Russia troops tightened their grip on Crimea as huge political rallies were held across the country.
ITV News Europe Correspondent Emma Murphy reports from Donetsk in eastern Ukraine:
An armed pro-Russian force wearing plain military uniforms sealed off another military airport in Ukraine's Crimea, a defence ministry spokesman on the peninsula said.
The 80 or so-strong group, who were supporting 50 civilians, blocked off the entrance to the airport near the village of Saki and established machine-gun posts along the landing strip, spokesman Vladislav Seleznyov said.
An object found floating in the sea could be an aircraft door belonging to the missing Malaysian Airlines plane.
It was spotted by a Vietnamese Navy plane taking part in the search.
Officials investigating the disappearance are narrowing the focus of their inquiries on the possibility that it disintegrated in mid-flight.
Pro-Russian protesters took down a Ukrainian flag outside a regional government's office in Eastern Ukrainian city of Donetsk, replacing it with the red blue and white flag of Russia.
Pockets of violence were reported across Ukraine, as thousands of pro and anti-Russian protesters held rival rallies in the main cities of Crimea.
Clashes flared in Sebastopol, when pro-Russian activists and Cossacks attacked a group of Ukrainians.
Thousands gathered at Kiev's Independence Square to mark the 200 anniversary of the birth of a poet and national hero Taras Shevchenko, protesting against Russia's involvement in Crimea.
Around 1,000 anti-fracking demonstrators have marched through Manchester in what organisers described as a "party atmosphere".
The protesters gathered in Piccadilly Gardens, in the city centre, before moving to Cathedral Gardens for speeches.
The event is thought to have been one of the biggest protests yet in the UK against the controversial shale gas extraction process.
Those taking part included members of the protest camp at Barton Moss, in Eccles, Salford, where test drilling is being carried out.
Greater Manchester Police tweeted:
Thanks to those who organised or took part in today's protest - around 1,000 people took part and we didn't have to make any arrests
Julian Assange said WikiLeaks will soon release a new batch of secret information.
The WikiLeaks founder spoke to a crowd of around 3,000 people via Skype at the South by Southwest Interactive conference in Austin in Texas.
He did not reveal any more details, saying he doesn't want the authorities to have time to prepare ahead of the release.
Mr Assange has been living at the Ecuadorian the embassy in central London for more than a year and half in a bid to avoid deportation to the US over the biggest leak of classified documents in US history.
Gravesend in Kent was the warmest spot in the country, recording a temperature of 20.5C (68.9F) at 2.30pm today, according to the Met Office.
The last time the 20C mark was breached in Britain was on October 8 last year.
The United States will not recognise the annexation of Crimea by Russia if residents of the region vote to leave Ukraine in a referendum next week, US national security official Tony Blinken said.
US Secretary of State John Kerry has previously warned his Russian counterpart Sergei Lavrov that any steps taken by Russia to annex Ukraine's eastern region of Crimea, would close the door to diplomacy.