BBC News with Jerry Smit

Just hours after Russian and Crimean leaders signed a treaty incorporating the Black Sea Peninsula into the Russian Federation, there have been clashes at a military base in Simferopol. The Ukrainian military says one of its servicemen has been killed and another injured. The Defence Ministry has now given servicemen the right to use weapons to protect themselves. In Kiev, Prime Minister Arseniy Yatsenyuk said the conflict over Crimea had moved from a political to a military stage. He described the annexation as a war crime.

“Now the conflict is shifting from a political to a military phase. Russian soldiers have started shooting at Ukrainian servicemen. ”

Ukraine had said it would never recognize Crimea joining the Russian Federation.

The United States has condemned Russia's intervention in Crimea, calling it a land grab and a continuing assault on Ukrainian sovereignty. The American Secretary of State John Kerry said President Obama could not stand by and do nothing.

“The President has made it clear that if there is this move to the full annexation which appears to be clearly the direction that they have decided to move, it will be unfortunate. And it will not be, because we want to create some kind of confrontation, but because there is no choice but to enforce the standards that the international community has worked on for so long.”

The US is promising further sanctions against Russia, a day after targeting the finances of seven senior Russian officials. David Willis reports from Washington.

President Obama's decision to impose asset freezes and travel bans on nearly a dozen Russian and Ukrainian officials led to a mockery from some of those involved, including Russia's deputy Prime Minister Dmitry Rogozin, who took to Twitter to point out that he didn't have property or a bank account overseas. However Jay Carney told reporters that the sanctions were costing Russia, and confirmed the administration was looking to target those closest to the Russian government and Russian arms dealers in a further round of measures.

The Russian Foreign Minister Sergei Lavrov said the sanctions that had already been imposed were unacceptable and threatened consequences. In a speech at the Kremlin, President Putin strongly defended Russia's annexation of Crimea, and called on the United States to stop what he called the hysteria and rhetoric of the Cold War.

An Islamist website in Russia is reporting the death of the Chechen leader of the insurgency in the north Caucasus. The site said, Doku Umarov, whom the media had nicknamed Russia's Bin Laden had become a martyr, but did not give the details of how he died. Russia's National Anti-terrorism Committee said it could not confirm Mr. Umarov's death. His group has been blamed for a string of bombings in recent years, including two attacks on Moscow.

World News from the BBC

The families of Chinese passengers who aboard the missing Malaysia Airlines flight have expressed anger of what they say is the lack of support and information. One woman said relatives were facing mental breakdowns. From Beijing here's Damian Grammaticas.

Frustrations in Beijing are mounting. At the daily briefing by Malaysia Airlines officials, some of the Chinese families desperate to hear something definite, lost their tempers. A few threatened a hunger strike, convinced that the truth has been kept from them. China's government too isn't giving them much information or support. In Malaysia, investigators are now unsure that it was someone on board who turned off the communications systems and turned the plane westwards. They are reconsidering mechanical failure as a possible cause for the disappearance of the aircraft.

The medical charity MSF has issued dire warnings about the plight of refugees fleeing the Central African Republic. A doctor in a refugee camp in neighboring Chad says that nearly half the patients he deals with are hungry. Another doctor spoke of children arriving with head wounds. The charity says many women have been forced into prostitution to feed their children.

United States has broken up a large online child pornography ring and arrested 14 people. Officials said more than 250 children have been exploited in the US and five other countries. A government spokesmen said they'd never before identified as many victims in one investigation.

The Rolling Stones have called off their tour of Australia and New Zealand following the death on Monday of lead singer Mick Jagger's long-time girlfriend L'Wren Scott. The group said they hoped their fans would understand the reason for their decision and hoped to reschedule the concert. Mrs. Scott was found dead in her apartment in New York. In a statement, Mr. Jagger said he was struggling to understand Mrs. Scott's apparent suicide.

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