BBC News with Nick Kelly.

The United Nations has demanded an immediate ceasefire in South Sudan saying that escalating violence could destroy the fabric of the world's newest nation. The two warring factions are preparing for peace talks in Ethiopia but fighting has continued. Nearly 200,000 people have fled their homes since fighting broke out last month between supporters of President Salva Kiir and his former deputy Riek Machar. Ours correspondent Alastair Leithead has just reached the camp for refugees from the town of Bor which is seeing intense fighting.

The people of Bor fled the only way they could across the Nile. Tens of thousands of them are now camped out here along a broad swath at the river bank, and at each one of the trees that scattered the landscape, a family has set up a home. They brought only what they could carry, they move fast and in fear, now the food is almost gone, the dirty Nile water is causing sickness and diarrhea which is overwhelming the small emergency clinic being run by Medicins Sans Frontier.

At least two car bombs have exploded outside a hotel in the Somali capital Mogadishu; at least eight people are reported to have been killed. The hotel Jazeera near the airport in Mogadishu is popular with Somali politicians. The Islamist militant group al-Shabab which was driven out of Mogadishu in 2011 said it carried out the attack.

Doctors treating the former Israeli Prime Minister Ariel Sharon say there has been a serious deterioration in his condition. Kevin Connolly reports from Jerusalem.

Ariel Sharon has been in a coma for almost exactly eight years since he suffered the brain haemorrhage in January in 2006. In recent days, he is understood his condition is deteriorated and doctors are believed to be discussing the prospect of medical intervention with members of the former Prime Minister's family gathered at his bedside. Many Israelis, even some who didn't support him during his political career, admired his military record. All of a soldier and statesman, he has been frequently controversial. In the Arab World, he was hated for ever associated with the massacre of Palestinians in refugee camps during Israel's invasion of Lebanon in 1982. He is one of the last leaders of Israel's founding generation and many in the country were following the news of his declining health with a real sadness.

The new Mayor of New York Bill de Blasio has issued his formal swear-in ceremony to outline what he calls his progressive aims for the city. He is the first Democratic Mayor of New York in more than two decades. Mr. De Blasio has said the government had to try to end social and economic inequality.

"Those of us here today, and millions of everyday New Yorkers in every corner of our city, you must continue to make your voices heard; you must be at the centre of this debate. And our work begins now."

World News from the BBC.

There have been more clashes between Muslim and Christian militia in the Central African Republic where at least 1,000 people were killed last month. Residents of the capital Baugui described seeing groups of Muslims throwing grenades and setting fire to the homes of Christians who then launched the revenge attacks.

The head of the Palestinian mission in the Czech capital Prague has been killed in an accidental explosion at his residence. Police say the diplomat Jamal al-Jamal was killed when opening an old booby-trapped safe. Robert Cameron has more details.

Jamal al-Jamal had only presented his credentials in October and had spent just two nights at his residence at a newly-built diplomatic complex in the northern suburb of Prague. The Palestinian Foreign Minister Riad Malki told the AP news agency that Mr. Al-Jamal had decided to open an office safe that had been sealed for 30 years for reasons unknown. This triggered an explosion causing severe injuries to Mr. Al-Jamal's head, chest and abdomen. He died several hours later in hospital.

Thousands of Ukrainian nationalists have held a torch-lit rally in the capital Kiev. The marchers from the far right Freedom Party were marking the birthday of a World War II-ear Ukrainian partisan leader. The party has been a key participant in recent protests in Kiev where thousands of demonstrators against President Viktor Yanukovych's decision to cancel a deal with the European Union in favour of closer ties with Russia.

And people have been queuing up to buy marijuana in Colorado, the first American state where it's becoming legal to grow and sell the drug for recreational use. More than 20 shops are now licensed to sell limited amounts to people aged over 21. Several reported long queues and at one shop in Denver, people cheered as the first person made their purchase. Some kind of users held parties to celebrate the change in the law which was approved in November 2012.

BBC News.