Officials in Yemen say 16 people have been arrested for illegal separatist activities in three southern provinces.
They're accused of taking part in unauthorised protests and jeopardising security.
Some group members were carrying anti-government leaflets and banners, and others had attacked security forces with stones, security sources said.
The government of Yemen, the poorest country in the Arab world, is battling a Shi'ite insurgency in the north, separatists in the south, and attacks by a resurgent al-Qaeda.
People in the south, home to most of Yemen's oil facilities, have long complained that northerners have abused a 1990 agreement that united the country to seize their resources and discriminate against them.