At least two policemen have been killed in clashes with separatist rebels in southern Yemen, it has been reported.
A further five people were reported wounded in fighting in Zinjibar after demonstrations against President Ali Abdullah Saleh's government.
Southern separatists say that their region, a separate country before 1990, is being exploited by northern Yemen.
A truce with northern rebels has allowed the government in Sanaa to turn its attention to the secessionists.
The fighting erupted when security forces tried to arrest an arms dealer suspected of supplying the separatists, the news agency Reuters quoted government officials as saying.
The man was named by news agencies as Ali Saleh al-Yafei, a prominent secessionist leader.
Last week around 20 people were arrested in the southern region and charged with rioting, which sparked Sunday's demonstrations across Abyan province.
Southern Yemen is home to most of the country's oil infrastructure.
Analysts say there has been rising tension throughout the south in the past two years, as the southern independence movement gains strength.