At least 95 people have been killed and 158 were wounded in a powerful suicide blast in the Afghan capital, Kabul.

The Taliban claimed responsibility for Saturday's assault, the third major attack in the past seven days. An interior ministry spokesman blamed the the Taliban-affiliated Haqqani network, which has been behind many of the biggest attacks on urban targets in Afghanistan.

Attackers blew up an explosives-packed ambulance near an interior ministry building on a busy and heavily-guarded street in Kabul's centre in the afternoon. The Jamhuriat hospital, government offices, businesses and a school are close to the site of the blast.

Ahmed Naweed, a witness, told Al Jazeera the attack took place between two checkpoints.

"There were many dead bodies and blood everywhere," he said. "People were crying and screaming and running away."

Al Jazeera's Jennifer Glasse, reporting from Kabul, said Afghan officials were calling the attack a "massacre".

"In the immediate aftermath of the attack, we saw bodies scattered across the street," she said. "The hospitals are inundated with the wounded and officials fear the death toll may rise."

The driver passed through one checkpoint by telling police he was escorting a patient to the hospital, our correspondent said, and detonated the explosives at the second.

Huge plumes of dark smoke rose over the city following the attack, and vibrations of the explosion could be felt several kilometres away, according to witnesses.

Emergency vehicles rushed to the city centre, TOLO news reported.

United Nations Assistance Mission in Afghanistan said attackers must be brought to justice.

"Today's attack is nothing short of an atrocity, and those who have organised and enabled it must be brought to justice and held to account," Tadamichi Yamamoto, head of the UNAMA, said in a statement.

The incident comes a week after a Taliban-claimed attack on the Intercontinental Hotel in the city, which left more than 20 dead, and days after the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) killed at least three people at the office of Save the Children in Jalalabad.

Commenting on Saturday's bomb blast, Dejan Panic, coordinator at a hospital run by the Emergency NGO, said: "It's a massacre."

The organisation tweeted a photo of a makeshift medical ward, where patients were being attended to on the floor.

At least seven people were dead on arrival, Emergency said.

#Kabul. Over 70 wounded, 7 dead on arrival transferred at @emergency_ong hospital after the attack. “It’s a massacre”, said Dejan Panic, coordinator in@#Afghanistan. pic.twitter.com/IZ2FFMO11Y — EMERGENCY (@emergency_ong) January 27, 2018

Abdullah Fahimi, a Kabul-based researcher, told Al Jazeera that the attack could be in response to the government's recent efforts to pound the Taliban in remote areas, in addition to recent US sanctions on its members.

Fahimi explained: "This is an impasse, neither side is winning. The [Taliban] group is not going to surrender or give up, they want to take more areas, territories."

On Friday, the administration of US President Donald Trump sanctioned four Taliban and two Haqqani network leaders "who have been involved in attacks on coalition troops, smuggling of individuals, or financing these terrorist groups", said Sigal Mandelker, under secretary for terrorism and financial intelligence, a position within the US treasury department.

Afzal Ashraf, visiting fellow at Nottingham University's Centre for Conflict, Security and Terrorism, said the Taliban's aim was to tell the international community that it "remains a force to be reckoned with".

The Trump administration's strategy of sending more troops to Afghanistan and increasing air strikes there was "clearly not working", he said.

"The solution has to be political," he said, adding: "And I'm afraid the same amount of effort hasn't been put into providing a political solution, while politicians tasked with delivering a more attractive form of government in Afghanistan than the Taliban haven't been able to provide that counterbalance.

"That is part of what has emboldened the Taliban."

With reporting by Al Jazeera's Shereena Qazi: @ShereenaQazi