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Ukrainian authorities said the country's top security body and a national news agency had been hit by cyber attacks.
Unidentified sources launched denial of service (DoS) attacks which are intended to make a machine or network resource unavailable to its intended users, officials said.
Last week the country's telecommunications system had come under cyber attack, with some Internet and telephone services severed after Russian forces seized control of airfields and key installations in Ukraine's Crimea region.
International military observers from the Organisation for Security and Cooperation in Europe said "warning shots" were fired as the mission turned back trying to enter Crimea.
Military assessment visitors from OSCE States turned back from Crimea checkpoint at Armyans'k. Warning shots fired. Everyone safe. #Ukraine
The OSCE observers have been unable to enter Ukraine's Crimea peninsula for the second day in a row.
David Cameron was among a host of names congratulating Britain's Jade Etherington, after the the British skier won the women's visually impaired downhill:
Proud of Jade Etherington, who won silver in the women's visually impaired downhill in Sochi. #GoParalympicsGB.
A host of others took to the social network to tweet their thanks. Eventually, Etherington herself tweeted, though her celebrations were understated:
We've won a Downhill medal!!!!!!! It's Silver :))))
The Liberal Democrats will make raising the personal income tax allowance to £12,500 a key demand in any coalition negotiations after the 2015 general election.
Treasury Chief Secretary Danny Alexander confirmed in a speech to the party's spring conference that increasing the threshold will be written into the party's manifesto for the contest.
A rise of at least £500 - giving a tax cut of £100 - would be earmarked for the first Budget after the election, he said.
The Lib Dems have made raising the point at which people start paying income tax to £10,000 a priority in Government and Mr Alexander indicated pressure was mounting for George Osborne to signal a further rise to £10,500 in this month's Budget.
Air search and rescue mission in the area where a Malaysian plane carrying 239 people went missing has been suspended, the Malaysian Airlines operating the flight said in a statement.
The airline said seaborne rescue teams from Malaysia, Singapore and Vietnam will continue searching the South China Sea.
The plane disappeared from radar at 1.30am local time (5.30pm GMT) on a flight from Kuala Lumpur to Beijing.
A large military convoy has been pictured entering Simferopol in southern Crimea.
ITV News' Matt Brindley tweeted: "Large military convoy enters Simferopol. The vehicles have no number plates.
"They've come from east Crimea and appear to be heading around Simferopol and then to the north."
Poland's foreign minister says the country is to evacuate its consulate in Crimea due to "disturbances" from Russian forces.
Because of continuing disturbances by Russian forces there, we have reluctantly evacuated our consulate @plinsevastopol in Crimea, Ukraine.
Russian Foreign Minister Sergei Lavrov said Ukraine's interim government "gets its orders from radicals" and that Western supporters should "bring them to reason."
"They are trying to represent us as a conflicting side, which we are not. This conflict is of an inner-Ukrainian nature, inspired from outside, and not from our side," Mr Lavrov said.
The temporary government, as you called it, is not independent. Unfortunately, it depends on radical nationalists, who took power in an armed coup," he added.
Vince Cable has stepped up his row with the Tories over immigration, accusing his coalition colleagues of tending to "fan the flames of prejudice" over the issue.
Ministers have come under pressure to disclose their own use of foreign domestic help after Immigration Minister James Brokenshire deplored the effects of the "metropolitan elite" using cheap migrant workers.
Mr Cable called for changes to make it easier for foreign students to stay and work in the UK, and for immigrants to bring their families to live with them.
Liberal Democrat Chief Secretary to the Treasury Danny Alexander today also hit back at Mr Brokenshire's comments, which he described as "incredibly dangerous".
Mr Alexander defended his own employment of a Portuguese cleaner, while David Cameron was also forced to answer questions over his family's hiring of a Nepalese nanny.
After a cloudy start to the weekend cheering up this afternoon with brighter skies developing as clearer air seeps in from the continent.
Scotland and Northern Ireland and parts of the north-west will be prone to more cloud but to the east of high ground brighter breaks will develop.
Mild for the time of year - with possible 16 or 17 Celsius in the south.