Two suicide bomb attacks struck Yemen security buildings in the government-held bastion of
Aden on Sunday, killing at least five members of the security forces and sparking clashes.
An explosives-rigged car driven by an al-Qaeda operative was detonated outside the security headquarters in the central district of Khor Maksar in Aden where the
internationally recognised government of President Abd Rabbo Mansour Hadi is based, a high-ranking security official said.
Moments later, gunmen stormed the Aden criminal investigations unit and set fire to files and archives as a suicide bomber detonated an explosive belt in the building, a source in the unit said.
The twin attacks brought an abrupt end to a period of relative calm in Aden, where the
Saudi-backed Hadi government has been based since being driven out of the capital Sanaa by Houthi rebels in 2014.
Yemen's war has allowed al-Qaeda in the Arabian Peninsula (AQAP) to flourish in the south of the country.
In recent weeks, Yemeni forces allied with a Saudi-led coalition have closed in on
AQAP strongholds and driven them out of pockets of the southern provinces of Abyan and Shabwa.
The United States, which considers AQAP the most dangerous branch of al-Qaeda, also regularly conducts drone strikes on southern Yemen.
Yemen's conflict escalated in 2015 when a Saudi-led coalition launched a military intervention aimed at rolling back Houthi gains and restoring Hadi to power.
The fighting has caused a humanitarian catastrophe which the UN says is the world's worst, pushing seven million people to the brink of famine and sparking a cholera outbreak that the World Health Organisation says has killed 2,000 people.
More than 10,000 civilians have been killed in the conflict and thousands more have been injured.
Yemen is today split in two, with the Houthi-Saleh camp controlling the north and coalition-backed pro-government forces in the south.