MOGADISHU, Somalia May 18 (Garowe Online) - At least 17 people were killed Sunday afternoon in the Somali capital Mogadishu after a mysterious explosion occurred at a house where militants were lacing vehicles with explosives, independent sources tell Garowe Online.

One source close to Al Shabaab hardliners confirmed that four foreigners were among the dead, but he declined to name the victims' countries of origin.

"An explosive device that was connected badly to two Toyota trucks exploded accidentally, killing everyone around and destroying the house," the source said.

The house was located in Daynile district, in the outskirts of Mogadishu, he added. Neighbors were forced to stay inside their homes and onlookers were prevented from coming anywhere close to the house by Al Shabaab gunmen.

Neither the Somali interim government nor Al Shabaab have spoken out publicly regarding the mysterious blast that was heard at faraway locations.

Al Shabaab hardliners have boasted that foreign fighters from across the Muslim world are fighting among their ranks as they attempt to overthrow the U.N.-backed interim government led by President Sheikh Sharif Ahmed.

The group has previously claimed responsibility for suicide bombings using explosives-ladden vehicles, a tactic imported to Somalia from wars in Afghanistan and Iraq.

The U.S. government considers Al Shabaab to be a terrorist organization, but the Islamist group controls most regions in south-central Somalia.

President Sheikh Sharif's interim government is the 15th attempt to restore national order in Somalia since the outbreak of civil war in 1991.

Source: Garowe Online