North Korea likely took meticulous steps to conceal any residue from its February nuclear weapon test, fueling suspicions that it is using a new bomb design with highly enriched uranium at its core, The Washington Post reported Sunday.

Citing unnamed U.S. officials and weapons experts, the newspaper said the effects of the February 12 explosion were remarkably well contained, with few radioactive traces escaping into the atmosphere.

The U.S. military said Monday it had deployed stealth fighters to South Korea as part of an ongoing joint military exercise that has triggered dire North Korean threats of armed retribution.

Two F-22 Raptor fighters arrived in the South on Sunday to participate in the annual "Foal Eagle" exercise that will last until April 30, a spokesman for the U.S. forces in South Korea told Agence France Presse.

Malian troops swept Timbuktu for remaining Islamist fighters after a weekend battle that left seven dead and forced France to dispatch reinforcements and fighter jets to help Mali's army.

By late Sunday relative calm had been restored, after Islamist militants used the chaos created by a suicide bombing Saturday night to infiltrate the city and engage French and Malian troops in a day-long battle that left four more rebels, a soldier and a civilian dead.

A worker was killed and three others were injured Sunday during an industrial accident at a U.S. nuclear power plant that did not release any nuclear material, officials and operators said.

Part of a generator fell as it was being moved out of the turbine building at Entergy Operations Inc's Arkansas Nuclear One in Russellville, the company said in a statement.

Nicolas Maduro was speechless when Hugo Chavez first told him he may have to carry on the Venezuelan leftist leader's legacy, but he now insists the "revolution is united" behind him.

The acting president, a veteran of Chavez's inner circle now hoping to succeed him in April 14 elections, described how his mentor handpicked him to lead the so-called "Bolivarian Revolution" in an exclusive interview with Agence France Presse.

The Central African Republic's Prime Minister Nicolas Tiangaye on Sunday named his new post-coup government mostly made up of rebels and members of the former opposition after being brought back by self-proclaimed president Michel Djotodia, under a decree read on national radio.

The 34-member cabinet includes nine ministers from the rebel Seleka coalition that has been in power for a week, eight from the former opposition and one close to ex-president Francois Bozize. The other 16 are largely unknown.

North Korea vowed Sunday to strengthen its nuclear weapons, a day after announcing it is in a "state of war" with South Korea, and said it would never trade its atomic deterrent for aid.

Tensions have risen sharply since the United Nations tightened sanctions in response to the North's nuclear and missile tests, and since the United States and South Korea launched military drills south of the border.

Soldiers raided a suspected hideout for Islamist extremist group Boko Haram in northern Nigeria's largest city of Kano on Sunday, sparking a clash that left 15 people dead, the military said.

The military claimed that those killed included 14 Islamists and one soldier, while alleging the extremists were planning an Easter day attack in the city.

Afghan President Hamid Karzai held talks Sunday with the emir of Qatar during a visit to discuss opening a Taliban office in the Gulf state, as a prelude to a possible peace deal with the militants.

Karzai discussed "issues of mutual interest" with Sheikh Hamad bin Khalifa al-Thani, state news agency QNA said, without giving details of the low-profile meeting in Doha city.

Malian troops backed by French forces on Sunday clashed with Islamist fighters who had infiltrated the northern city of Timbuktu, leaving two jihadists dead and four Malian soldiers wounded, a Malian army officer said.

"Jihadists have infiltrated the center of Timbuktu... Our men are currently fighting them with the support of a unit of our French partner," the Malian officer told Agence France Presse by telephone.