MOGADISHU (Reuters) – Suicide bombers killed at least 13 people at the gates of the African Union’s main peacekeeping base in the Somali capital Mogadishu on Tuesday, police said, in an attack claimed by the Islamist militants of al Shabaab.

The force of the explosions shattered windows at the nearby airport, showered arriving passengers with glass and forced the suspension of flights, police and witnesses said.

Police said the first attacker detonated a car bomb and the second tried to storm the base on foot, but was shot and exploded at the gate.

“At least 13 people mostly security forces died in the two car bomb blasts,” and 12 others were wounded, Abdiqadir Omar, a police officer told Reuters.

The guards were caught in the blast as they escorted U.N. personnel into the base, which is known as Halane, he added.

Al Shabaab, an Islamist militant group linked to al Qaeda and fighting to topple Somalia’s Western-backed government, said it set off two car bombs.

The African Union’s AMISOM force said on Twitter it condemned the “senseless attacks that aim to disrupt and cripple the lives of ordinary Somalis”. There was no immediate comment from the United Nations.

People arriving on international flights said the blasts shattered windows in the airport buildings.

“We were greeted by two loud blasts. The glass of the airport building fell on us,” said Ali Nur, who had just got off a plane from Nairobi.

Al Shabaab regularly attacks AMISOM, which is made up of about 22,000 military personnel from Uganda, Kenya, Ethiopia and other African countries helping to support Somalia’s government and army.

The country in the Horn of Africa was plunged into anarchy in the early 1990s following the toppling of military dictator Mohamed Siad Barre.

(Reporting by Abdi Sheikh and Feisal Omar; Writing by Duncan Miriri and Elias Biryabarema; Editing by Andrew Heavens)