Update:

The death toll from the 14 October truck bombing in Somalia's capital is now over 300, the director of an ambulance service said Monday, as this country reeled from the deadliest single attack it's ever experienced.

Saturday's truck bombing targeted a crowded street in Mogadishu, and about 300 others were injured. Somalia's government is blaming the al-Qaida-linked al-Shabab extremist group, which has not commented.

The attack was one of the worst in the world in recent years. It is one of the deadliest attacks in sub-Saharan Africa, larger than the Garissa University attack in Kenya in 2015, in which 148 died, and the U.S. Embassy bombings in Kenya and Tanzania in 1998, in which about 219 were killed.

Original report:

At least 276 people have been killed and around 300 injured following a double truck explosion in Somalia's capital of Mogadishu, with authorities believing the number of confirmed casualties will rise further.

President Mohamed Abdullahi Farmaajo declared three days of national mourning following what is believed to be the deadliest attack ever seen in the country, thought to have been carried out by the al-Shabab terrorist group.

Police say the first explosion occurred outside the Safari Hotel in the busy K5 intersection, flattening nearby buildings in the process. The blast took place close to Somalia's foreign ministry building.

A second explosion occurred around two hours later in the capital's Median district.

Dr Mohamed Yusuf, the director of Medina hospital, said: "The hospital is overwhelmed by both dead and wounded.

"We also received people whose limbs were cut away by the bomb. This is really horrendous, unlike any other time in the past."

Mogadishu resident Muhidin Ali told news agency AFP it was "the biggest blast I have ever witnessed, it destroyed the whole area".

Police official Ibrahim Mohamed told AFP: "It is very difficult to get a precise number because the dead bodies were taken to different medical centres and some of them [were taken] directly by their relatives for burial."

Rescue workers have been continuing the desperate search for survivors since the explosion on 14 October.

The International Committee of the Red Cross (ICRC) says four volunteers with the Somali Red Crescent Society (SRCS) are among the dead.

Jordi Raich, International Committee of the Red Cross Head of Delegation said: "Thousands of civilians lose their life in Somalia every year as a direct consequence of the ongoing conflict.

"SRCS and the ICRC remind all parties that civilians are protected by international and customary laws and must be respected at all times".

While al-Shabab have not yet claimed responsibility, the group have committed repeated attacks against the UN-backed government and its African Union allies as part of a bid to topple the administration and impose its own strict interpretation of Islam.

The militants had controlled the Somali capital between 2007 and 2011 before being forced out during the ongoing conflict.

In a statement, the US Mission to Somalia said: "Such cowardly attacks reinvigorate the commitment of the United States to assist our Somali and African Union partners to combat the scourge of terrorism."

Mogadishu explosion Somalia truck bomb
A man runs past the scene of the explosion in Mogadishu, Somalia REUTERS/Feisal Omar