Kabul on high alert after ambulance bomb toll tops 100

People attend the funeral of one of the victims of a suicide bomb attack, in Kabul, Afganistan, on Sunday. 28 January 2018. (EPA photo)

Afghanistan Sunday declared a day of national mourning as the toll for those killed by a huge bomb hidden in an ambulance in Kabul topped 100 people, sharply raising tensions after insurgents struck in the city for the second time in a week.

At least 103 people were killed and 235 wounded in Saturday's lunchtime attack claimed by the Taliban, which caused panic in the war-torn capital and overwhelmed its hospitals.

Kabul remained on high alert as the presidential palace declared a national day of mourning for Sunday, with flags flying at half-mast. The attack was one of the worst to strike the capital in recent years.

Central Kabul was unusually quiet on Sunday, a normal workday in Afghanistan, with little traffic and few people on the street.

In contrast, security checkpoints have been beefed up, particularly in the streets near the blast scene, as the city braced for the possibility of further violence.

A security alert issued on Sunday warned that the Islamic State group -- which claimed a deadly attack on Save the Children's office in Afghanistan's east on Wednesday -- was planning to attack supermarkets and shops in Kabul frequented by foreigners.

US President Donald Trump called for "decisive action" against the Taliban over the assault as other international leaders also condemned the attack.

Afghan authorities gave an updated toll Sunday for those killed and maimed in the huge blast.

"Unfortunately a number of wounded people have died in hospital. The number of martyrs is now 103 and wounded is 235," Interior Minister Wais Barmak told reporters.

Health ministry spokesman Waheed Majroh told reporters earlier Sunday that most of the injured were men.