The Yemeni branch of the al-Qaeda terrorist organization has claimed responsibility for an attack on a police academy in the capital Sanaa on Wednesday which killed at least 20 people, Xinhua reported.

"We claim responsibility for the bombing of the police academy in Sanaa," al-Qaeda said, Xinhua reported.

The blast occurred as police cadets were leaving the academy building after classes, Al Jazeera news agency said.

According to witnesses, a suicide bomber approached the academy in a taxi which was then was totally destroyed by the blast.

Al Qaeda in the Arabian Peninsula (AQAP), has been described by U.S. officials as the most active branch of the global militant network. In May, it claimed responsibility for killing about 100 people at a military parade in Sanaa.

In November 2010, the group claimed responsibility for a cargo plane crash in the United Arab Emirates as well as sending parcel bombs found in London and Dubai.

Meanwhile, the Yemeni government said two al-Qaeda fighters who escaped from prison last month were re-arrested in a southern province, Al Jazeera said.

One of them, Nasser Ismail Ahmed Muttahar, was detained for taking part in an attack on the US Embassy in Sanaa in 2008, the agency said.