BBC News with Marion Marshall.

The President of South Sudan Salva Kiir and the rebel leader Riek Machar have signed a deal in the Ethiopian capital Addis Ababa to cease hostilities within 24 hours. The talks were the first time the 2 men had met since fighting broke out in South Sudan in December. Emmanuel Igunza has the details.

This is a really huge step in such aim finding a solution to the political crisis and the bloody conflict that has engulfed South Sudan for the past 5 months. And this has been so important because they say there would be a next talk, both teams have been agreed to a ceasefire. They have also undertaken to issue orders to the military commanders on the ground in South Sudan to stop all combat and to allow humanitarian aid to get to those people, 3 million people in need of emergency food aid in South Sudan. So allowing that, food should get to them.

The United States has sharply criticized President Putin's visit to Crimea, his first since Russia annexed the territory from Ukraine. The US State Department spokeswoman Jen Psaki, said the trip would worsen the situation in Ukraine.

Our view is that this trip is provocative and unnecessary. Crimea belongs to Ukraine, and we don't recognize, of course, the illegal and illegitimate steps by Russia in that regard.

The European Union and Nato have also condemned Mr. Putin's visit. Ukraine's foreign ministry said Russia was deliberately escalating the crisis in the region.

Ukrainian security forces have clashed with pro-Russian protesters in the eastern city of Mariupol. Local officials say 7 people were killed and 39 injured, although Ukraine's interior minister earlier said more than 20 people had died. The government said a gun battle began when pro-Russian activists tried to storm a police station. Local witnesses have accused the security forces of opening fire on unarmed protesters.

Amnesty International says it has damning evidence that the Nigerian military failed to act on advanced warnings of the raid in which more than 200 school girls were kidnapped 25 days ago. Here is our security correspondent Frank Gardner.

Amnesty International has had a team on the ground in Nigerian for some time, gathering testimony from both government officials and members of the public. Their researcher, Makmid Camara says the military were warned of an impending attack by Boko Haram on the town of Chibok at 7 o'clock in the evening over 4 hours before it took place.

A special request was made for reinforcements when it was becoming evidently clear that the attackers were indeed on the way, but no reinforcement was then sent when the attack took place at 11:45.

The Nigerian information minister Labaran Maku told the BBC he doubted the Amnesty report, but would investigate it. Meanwhile, British, US and other international teams of experts have arrived in Nigeria to help in the hunt for the missing girls.

World News from the BBC.

More than 20 years after it was destroyed during the conflict in the former Yugoslavia, Sarajevo's city hall housing the national library has reopened. The iconic building which was first inaugurated in 1896 was hit by a mortar and burned down during the Bosnian-Serb siege of city in 1992, it's been restored to mark the centenary of the World War I.

Yemeni security forces have fought a gun battle with militants outside the President Palace in the capital Sanaa. Sebastian Usher has this report.

Heavy gunfire resounded through Sanaa for around an hour as presidential security guards battled with militants. A security source said the gunmen had tried to force their way through the main gate of presidential palace as fighting raged there. An explosion was heard in another district of the capital near a building used by the security services. Officials quickly blamed al-Qaeda linked militants for the attacks. The day to night, earlier reports for the defence minister had survived an assassination attempt in the south where the army is mounting a new offensive against al-Qaeda, the group has lost towns it held and personnel but vowed retaliation.

Eleven former employees of Spain's state railway company have been made formal suspects in an investigation into last year's train crash in the city of Santiago that killed 79 people. They include a former director general of the company and a former head of safety. The train was traveling at more than twice the speed limit when it derailed on a bend.

Roman Catholic bishops in Argentina say the country is sick with violence and corruption comparing it to a cancer, causing injustice and deaths. In a statement released at their annual conference in Buenos Aires, the bishops also said violence in society was getting more ferocious than ever. The government of President Cristina Fernandez de Kirchner responded by saying this was a deliberate attempt to blame it for rising levels of insecurity.

BBC World Service News.