Nato's surveillance jets will monitor Ukraine crisis

Nato said today that it will deploy Awacs reconnaissance planes in Poland and Romania to monitor the crisis in Ukraine, as armed soldiers extended their grip on Crimea ahead of a planned referendum on transferring the Ukrainian region to Russian rule.

Read: The Awacs planes Nato is sending to monitor Ukraine

Britain's E-3D Awacs will join the Nato mission in Ukraine, the Ministry of Defence announced tonight, saying it was "only right" the UK undertakes its share of the mission.

A naval base in the Crimean town of Chernomorskoe was taken over by around 200 armed troops last night, with the leader of the base telling ITV News' International Correspondent John Irvine the men wore Russian uniforms and addressed each other using Russian army ranks.

Following the takeover, a new Crimean unit was sworn in at the local government offices, where troops have painted over the Ukrainian flag with Russia's national colours.

David Cameron told the House of Commons this afternoon that the referendum, planned for Sunday, was "illegal, illegitimate and will not be recognised by the international community."

Read: Crimea invites OSCE observers to Russia referendum

He said that international powers will meet in London tomorrow to devise a list of Russian figures who could face asset freezes and travel bans if Moscow fails to de-escalate the crisis.

The prime minister added that he has not ruled out reverting the G8 to a G7, without Russia, adding, "but let's hope that isn't necessary."

Read: Russia referendum result 'already decided by Moscow' says Tatar leader

The US said Secretary of State John Kerry will hold talks with Russia's Foreign Minister Sergei Lavrov this week and may meet him, but first wants to see "concrete evidence" that Russia is prepared to engage on diplomatic proposals regarding Ukraine.

John Irvine reports from the naval based taken over by Russian troops in Crimea:

Tonight the press freedom watchdog Reporters Without Borders said that two Ukrainian journalists have been seized in Crimea, warning that those behind attacks on the media were trying to turn the region into a "black hole for news".