The African Union called Friday for a regional five-nation force of 7,500 troops to defeat the "horrendous" rise of Nigeria's Boko Haram Islamist militants.

The call for collective action came as leaders of the 54-member bloc opened their two-day annual summit in the Ethiopian capital Addis Ababa, where they were addressing a string of crises across the continent.

The White House on Thursday declined to describe Afghanistan's Taliban as a terrorist group, prompting consternation from the right, which accused President Barack Obama's administration of being out of touch.

"They do carry out tactics that are akin to terrorism, they do pursue terror attacks in an effort to advance their agenda," said White House spokesman Josh Earnest.

Efforts to improve ties with Cuba will not extend to handing control of Guantanamo Bay back to Havana, the White House said on Thursday.

"The president does believe that the prison at Guantanamo Bay should be closed down," said White House spokesman Josh Earnest. "But the naval base is not something that we wish to be closed."

An armed man appeared live on Dutch television on Thursday evening before being overpowered by police, images showed.

The man, speaking fluent Dutch and carrying what appeared to be a pistol, interrupted the NOS national broadcaster's 8 pm (1900 GMT) broadcast before being restrained.

A gas truck blew up outside a maternity hospital in Mexico City on Thursday, killing at least two people, injuring dozens and trapping others after the building crumbled.

Rescuers with dogs scoured the rubble of the Maternity and Children's Hospital in the Cuajimalpa borough for people who were stuck following the huge blast, which rocked the neighborhood.

Three American contractors were killed in an apparent "insider attack" at Kabul airport on Thursday, a U.S. defense official told AFP.

Details of the shooting remained unclear, said the official, who spoke on condition of anonymity. The victims, who were employed under a U.S. Defense Department contract to help train the Afghan air force, died from gunshot wounds.

The United States warned Russia on Thursday that it is mulling fresh sanctions over the fighting in Ukraine and welcomed an EU move to broaden existing measures imposed on Moscow.

State Department spokeswoman Jen Psaki said the agreement by EU foreign ministers to expand existing European sanctions "is just a further sign that the actions of the last several days and weeks are absolutely unacceptable and that there will be new consequences put in place."

U.N. Secretary-General Ban Ki-moon has decided to open an official inquiry on the shooting death of three protesters during demonstrations in northern Mali, his spokesman said Thursday.

Witnesses said the three Malians were shot in Gao by U.N. troops during protests on Tuesday against a U.N. plan to assert control over an area north of the town.

Britain said it had summoned the Russian ambassador Thursday after Russian military planes were found flying close to British airspace.

The move comes after a string of similar incidents and amid tense relations between Moscow and the West over the conflict in Ukraine and the killing in London of former Russian spy Alexander Litvinenko.

Nigerian fighter jets have bombed the northeast town of Malam Fatori, controlled by Boko Haram Islamists, the military said Thursday. 

Witnesses and some media reports said troops and air force planes from neighboring Chad were involved in the operation on Nigerian soil but Abuja neither confirmed nor denied the claim.