Authorities in Somalia's breakaway region of Somaliland arrested four French nationals who crossed into the territory from neighboring Djibouti, a government official said.

The four, among them women, were arrested on Thursday while driving in Bariisle village near the border and later handed back to Djibouti authorities.

Four American special operations personnel were killed over the weekend in the crash of their aircraft in Djibouti as it returned from a mission, the U.S. military said Monday.

The U-28, a modified single engine turbo prop plane used by special operations units, crashed Saturday near Camp Lemonnier, a base used by the U.S. military in the tiny Horn of Africa state.

U.S. Secretary of Defense Leon Panetta arrived in Kabul on Tuesday to reaffirm America's commitment to Afghanistan as Washington starts to withdraw combat troops and hand over security to Afghan forces.

The Pentagon chief, who says violence is falling in the country where the United States has been at war with the Taliban for 10 years, is slated to meet Afghan President Hamid Karzai and Defense Secretary Abdul Rahim Wardak.

The World Bank on Monday pledged more than $500 million (348 million euros) to aid the drought-stricken Horn of Africa region, as United Nations aid chiefs met in Rome to discuss ramping up relief efforts.

The bulk of the money will go towards long-term projects to aid livestock farmers while $12 million will be for immediate assistance to those worst hit by the crisis and facing starvation, the World Bank said in a statement.

Twelve million people in the drought-hit Horn of Africa region need emergency aid, the U.N. food agency said on Wednesday, appealing for $120 million to help desperate farmers.

"Around 12 million people in the Horn of Africa are currently in need of emergency assistance," the Food and Agriculture Organization said in a statement, adding that hundreds of people are dying every day in the crisis.

The plight of millions of people left hungry by a harsh drought across the Horn of Africa is set to worsen, with the rains not expected soon and harvests months away, a top U.N. official warned Saturday.

Scanty or failed rainfall in the region over the past two years has already forced thousands of Somalis to flee their country and ruined the livelihoods of millions in parts of Kenya, Ethiopia and Djibouti.