Prosecutors were questioning the four over the attack that killed the bomber and wounded three people, the website said.

Al Qaeda's Yemen-based regional wing claimed responsibility for the bombing, accusing the envoy of leading a war on Muslims in the Arabian Peninsula on Britain's behalf. Yemen has been a key Western security concern since the Yemen-based Al-Qaeda arm claimed responsibility for a failed December attempt to bomb a US-bound passenger plane.

Western countries want Yemen to deal with domestic conflicts and shift its focus to fighting Al-Qaeda.

Yemen has identified the bomber as a 22-year-old Yemeni, whose father said had been released from prison earlier this year but disappeared weeks before the bombing.