Clashes between Yemeni security forces and gunmen in the southern city of Aden on Tuesday left six civilians dead, a security official said.
The fighting erupted when security forces stormed a house in the Omar al-Mukhtar neighbourhood and arrested a man suspected of being a member of the Islamic State jihadist group, the official said.
Shortly after the operation, unidentified gunmen from the district attacked a checkpoint, triggering clashes that lasted for around three hours.
Three other civilians were wounded in the gunfight, the official said.
Aden serves as a temporary base for the government of President Abedrabbo Mansour Hadi as the capital Sanaa has been held by Houthi rebels since September 2014.
Despite several security campaigns, government forces in Aden appear to have failed to flush out jihadists who have taken advantage of the war with the Houthis to expand their presence.
Hadi, who is based in Riyadh, has occasionally visited the port city since loyalists backed by a Saudi-led Arab coalition pushed the Huthi rebels out of the city and four southern provinces in the summer of 2015.
Hadi fled Aden in March 2015 as the rebels closed in on his refuge, prompting a military intervention by the Arab coalition.