MOGADISHU, Somalia — The death toll from twin truck bombings in Somalia’s capital rose to at least 276 on Sunday, officials said, as emergency crews pulled more bodies from burned cars and demolished buildings after the terrorist blasts.

Officials called the explosions Saturday one of the deadliest attacks to hit the capital, Mogadishu, since an Islamic insurgency began in 2007.

The blasts left at least 300 others wounded, and families scrambled to find missing relatives amid the rubble and in hospitals. The toll was expected to rise.

As angry protesters gathered near the scene of the bombings, Somalia’s government blamed the Al Qaeda-linked Al Shabab extremist group for what it called a ‘‘national disaster.’’

However, Al Shabab, Africa’s deadliest Islamic terrorist group, often targets high-profile areas of the capital but did not immediately claim responsibility for Saturday’s attack.

Al Shabab earlier this year vowed to step up attacks after both the Trump administration and Somalia’s president announced new military efforts against the group.

Al Shabab recently increased attacks on army bases across the southern and central parts of the country.

A former internal security minister, Abdirizak Omar Mohamed, said by phone from Erdogan Hospital, where many of the dead and the injured had been taken, that, “At least 237 people were confirmed killed in yesterday’s attack. There are other people who possibly died of their wounds at other hospitals.’’

President Mohamed Abdullahi Mohamed declared three days of national mourning and called for donations of blood and funds to help the victims.

“Today’s horrific attack proves our enemy would stop nothing to cause our people pain and suffering. Let’s unite against terror,’’ Mohamed said on Twitter.

He added that flags would be flown at half-staff: “Time to unite and pray together. Terror won’t win.’’

“I call on our citizens to come out, extend help, donate blood, and comfort the bereaved,’’ said the president, who donated blood Sunday.

There was no immediate claim of responsibility for the attack.

Photos published by local news media showed scenes of carnage and devastation, with bodies and bloodied slippers and shoes scattered in the aftermath. Windows of nearby buildings were shattered. Overturned cars burned in the streets.

Some of the victims died in their cars and in public transportation vehicles.

“There was a traffic jam, and the road was packed with bystanders and cars,’’ Abdinur Abdulle, a waiter at a nearby restaurant, said Saturday. “It’s a disaster.’’

The US Mission to Somalia condemned the bombings, calling them “cowardly attacks’’ that “reinvigorate the commitment of the United States to assist our Somali and African Union partners to combat the scourge of terrorism.’’

The Qatar Embassy was severely damaged in the explosion, according to the country’s Ministry of Foreign Affairs, which added that the chargé d’affaires had been slightly injured.

The British ambassador to Somalia, David Concar, said on Twitter that the blast had been clearly audible from inside the British Embassy, saying it was “a time for unity and resolve.’’

Erdogan Hospital, one of six hospitals that received wounded victims, said at least 127 people had been brought there for treatment.

Senator Abshir Ahmed, deputy speaker of the upper house of the Federal Parliament, wrote on his Facebook page that he had been told by Dr. Mohamed Yusuf, director of Madina Hospital, that 218 bodies had been taken to that hospital.

At least 130 had been burned beyond recognition, Ahmed wrote.

On Sunday, Prime Minister Hassan Ali Khayre appointed a 16-member committee, including ministers, civil society leaders, and religious leaders, to arrange national funerals for the victims and to provide assistance to the wounded, according to his office.

The blast occurred two days after the head of the US Africa Command was in Mogadishu to meet with Somalia’s president, and after the country’s defense minister and army chief resigned for undisclosed reasons.

The Mogadishu bombing is one of the deadliest attacks in sub-Saharan Africa, larger than the Garissa University attack in Kenya in 2015 and the US Embassy bombings in Kenya and Tanzania in 1998.

Mogadishu, a city long accustomed to deadly bombings by Al Shabab, was stunned by the force of Saturday’s blast.

The explosion shattered hopes of recovery in an impoverished country left fragile by decades of conflict, and it again raised doubts over the government’s ability to secure the seaside city of more than 2 million people.

Rescue workers searched for survivors trapped under the rubble of the largely destroyed Safari Hotel, which is close to Somalia’s foreign ministry. The explosion blew off metal gates and blast walls erected outside the hotel.