Yemeni security officials say police have detained at least 5,000 migrants over the last 10 days who were attempting to cross to Saudi Arabia.

The officials said Wednesday that the migrants, most of them from African countries, are being held in overcrowded police stations across the southern city of Aden.

Aden's security chief, Shalal Shaye, says the migrants have launched a hunger strike. He says authorities are seeking assistance from the U.N. migration agency and aid groups.

The other officials spoke on condition of anonymity because they were not authorized to brief media.

Migrants from the Horn of Africa continue to travel to Yemen en route to jobs in the oil-rich Gulf despite the four-year war between a Saudi-led coalition and Iran-linked Houthi rebels.