BBC News with Sue Montgomery

It's been almost 24 hours since a Malaysian Airlines flight from Kuala Lumpur to Beijing was reported missing. But there's still no indication of what happened, despite an air in sea search. Earlier reports of two apparent oil slicks sighted off the Vietnamese coast have not been confirmed. Most of the 239 people aboard the plane were Chinese. Discrepancies on the passenger manifest have let some analysts to speculate about a possible terrorist attack. Here's John Sudworth with more from Beijing.

With more than 150 Chinese nationals on board, The Foreign Minister Wang Yi told reporters that it was being treated as a national emergency. Two men named as being on the passenger list are in fact reported to be safe and well. One Austrian and one Italian and both were said to have had their passports stolen while travelling in Thailand in recent years. If it is confirmed that those passports were used to board the plane, then it would of course be a potentially significant lead.

The United States has warned Russia that any moves to annex Crimea would close the door to diplomacy. In a telephone conversation, the American Secretary of State John Kerry has told his Russian counterpart Sergei Lavrov that Crimea is part of Ukraine and the Moscow should avoid military escalation. President Obama has been discussing the deepening crisis with world leaders. More than 50 international observers from the Organization for Security and Cooperation in Europe have been turned back as they tried to enter Crimea, as in previous occasions, they were stopped by pro-Russia paramilitaries. Ben Brown is in Sevastopol.

This was the third day running the team of international observers had tried to cross the border into Crimea, and the third day running, they've been turned back. This time though, there were some additional menace in the air. The armed men who stopped them fired warning burst of automatic gunfire. The fact of shots were fired, albeit as a warning, is likely to be seen as another show of Russian defiance in Crimea and another slap in the face for the international community.

The Untied States says it's deeply concerned about what is described as the recent escalation of violence in the Sudanese region of Darfur. There's been no word so far from Khartoum. Here's our Africa editor Mary Harper.

In a statement, the US State Department said government-allied militias had recently burned homes and attacked civilians near the town of Nyala, causing thousands of people to flee. The US said the Sudanese air force had been involved, and urged Khatoum to stop its campaign of aerial bombardments in Darfur. The US said the people of Darfur have suffered insecurity, violence and atrocities for far too long and that now was the time for peaceful resolution to the violence.

World News from the BBC

The Syrian government says it's seized a town from rebels near the Lebanese border as part of its efforts to block their supply lines. Sebastian Usher reports.

Battles continue to rage across Syria, some more significant than others. That's certainly how the Syrian government is talking up its recapture of the town of Zara. It's important to the government because it's near the border with Lebanon, from where rebel fighters run vital supply lines for weapons and reinforcements. President Assad's supporters are trying to block these, and may now be closed doing so. Since last month, they've been bombarding in Yabroud, some 40 kilometers south along the border. The storming of Zara maybe a foretaste of what's installed for that town's remaining residents. Opposition activists say some of those left in Zara were killed in their homes.

Several thousand people have marched through the Lebanese capital Beirut to demand the passage of law, protecting women against domestic violence. The rally coincides with International Women's Day. Lebanon is one of the most liberal countries in the Arab World, but there's no law protecting women from violence by their fathers, husbands or brothers.

Thousands of Venezuelan students and opposition supporters have gathered for an anti-government rally in the capital Caracas. The government has deployed thousands of security officers to prevent a planed march towards the food ministry. President Nicolas Maduro said all parties were invited to take part in a dialogue for peace. But the opposition has said any participation will be conditional on the release of detained students. At least 21 people have been killed in nearly a month of protests.

Italy has urged ArmaLite in the United States to withdraw an advertisement, showing an image of Michelangelo's David holding a rifle. The Italian Culture Minister Dario Franceschini said the government would take legal action against the company unless it immediately withdraws the campaign. He said the image of an armed David was not only offensive but also illegal.

BBC News