Two explosions have been heard outside Mogadishu airport in Somalia, in what was seemingly a suicide attack on the African Union Mission in Somalia (Amisom)'s headquarters.

Amisom confirmed reports of the explosions, which took place around midday local time (9am GMT) on 2 January, through their social media account. A number of photos shared on social media showed a cloud of smoke rising from Mogadishu Aden Adde airport.

"A suicide car bomb rammed into the checkpoint outside the Amisom base," Abdikadir Hussein, a police officer, told Reuters.

"There are Somali security forces at the checkpoint and it is too early to know the number of casualties."

Another police officer, Mohamed Ahmed, told Reuters that at least three members of the security forces died, and the death toll was likely to increase considering the strength of the explosions. "We believe al-Shabaab is behind the attack," he added.

Affiliated with al-Qaeda, the Islamist militant group al-Shabaab frequently carries out attacks involving suicide bombers and gunfire. Most recently, an attack against Mogadishu's port killed at least 16 people in December, and in November a car bomb exploded in a market, claiming at least 20 casualties. The site of the peacekeepers' high-security compound was also targeted in July, when suicide bombers attempted to storm the base of the mission.

African Union peacekeeping forces drove out the group from the Somali capital in 2011, but the group still controls vast parts of outlying rural areas in the country, from which it launches guerrilla operations.

In a statement, Amisom released information about the attack. It said a first car bomb attacked the checkpoint, allowing for the second one to pass through, towards the Medina Gate. Amisom forces then fired at the vehicle, which exploded approximately 200 metres from the gate.

"Amisom commends the Somali Security Forces and Amisom troops, whose effective and swift action defeated the enemy's intentions," the organisation wrote in a statement on Twitter.

The east African country of Somalia has recently held controlled elections, its first since 1989, as it struggles to recover from a brutal civil war and attacks perpetrated by the Islamist militant group.