WASHINGTON (AFP) - The White House condemned the "horrific terrorist" twin bomb blasts claimed by the Islamic State in Iraq and Syria (ISIS) extremist group that killed 41 people in Beirut on Thursday (Nov 12).

"Such acts of terror only reinforce our commitment to support the institutions of the Lebanese state, including the security services, to ensure a stable, sovereign, and secure Lebanon," National Security Council spokesman Ned Price said in a statement.

The attack on a busy shopping street in a Beirut stronghold of the Shiite movement Hezbollah was the worst such assault in years. The army said the blasts were carried out by two suicide bombers and that the body of a third, who had failed to detonate his explosive device, had been found at the scene of the second explosion.

"The United States condemns in the strongest terms today's horrific terrorist attacks in Beirut, Lebanon that killed dozens and wounded hundreds more," said Mr Price.

"We offer our deepest condolences to the families and other loved ones of those killed and injured in this violence.

"The United States will stand firm with the government of Lebanon as it works to bring those responsible for this attack to justice," he added.