At least 90 people were killed and hundreds wounded Wednesday when a massive truck bomb ripped through Kabul's diplomatic quarter, bringing carnage to the streets of the Afghan capital just days into the holy fasting month of Ramazan.

Bloodied corpses littered the scene and a huge cloud of smoke rose from the highly-fortified area which houses foreign embassies, after the rush-hour attack tore a massive crater in the ground and blew out windows several miles away.

Witnesses described dozens of cars choking the roads as wounded survivors and panicked schoolgirls sought safety. Men and women struggled to get through security checkpoints to search for loved ones.

It was not immediately clear what the target was. But the attack underscores spiralling insecurity in Afghanistan, where a military beset by soaring casualties and desertions is struggling to beat back the insurgents. Over a third of the country is outside government control.

See: Over 800 Afghan troops died in 2017 winter fighting: US watchdog

Hours after the explosion ambulances were still at the scene as rescue workers were digging bodies from the rubble.

“Unfortunately the toll has reached 80 martyred (killed) and over 300 wounded, including many women and children,” said health ministry spokesman Waheed Majroh, adding the figures would continue to climb as more bodies are pulled from the debris.

The interior ministry, which put the number of wounded at 320, said a suicide bomber had detonated an explosives-packed vehicle in Zanbaq Square around 8:30am. “More than 50 vehicles were either destroyed or damaged,” it said in a statement.

The ministry called on Kabul residents to donate blood, saying hospitals were in “dire need”.

There was no immediate claim of responsibility. The Taliban — currently in the midst of their annual “spring offensive” — tweeted that they were not involved and “strongly condemn” the attack.

The insurgent group rarely claims responsibility for attacks that kill large numbers of civilians.

The militant Islamic State (IS) group has claimed responsibility for several recent bombings in the Afghan capital, including a powerful blast targeting an armoured Nato convoy that killed at least eight people and wounded 28 on May 3.

Pakistan condemns attack

The Foreign Office said in a press release that the blast has caused damage to the residences of some Pakistani diplomats and staff, while some sustained minor injuries.

"Pakistan strongly condemns the terrorist attack in Kabul... that has caused loss of precious human lives and injuries to many," the FO said.

"Pakistan being a victim of terrorism understands the pain and agony that such incidents inflict upon the people and society."

The FO extended condolences to the government and people of Afghanistan and condemned "terrorism in all its forms and manifestations".

Embassies damaged

Manpreet Vohra, India's envoy to Afghanistan, told the Times Now television channel the bomb went off around 100 metres from India's embassy, one of several in the area.

“We are all safe, all our staff, all our personnel are safe. However, the blast was very large and nearby buildings including our own building have considerable damage in terms of broken glass and shattered windows and blown doors etc,” he said.

Indian Prime Minister Narendra Modi tweeted: “We strongly condemn the terrorist blast in Kabul. Our thoughts are with the families of the deceased & prayers with the injured.”

The explosion also shattered windows at the Japanese embassy. “Two Japanese embassy staffers were mildly injured, suffering cuts,” a foreign ministry official in Tokyo told AFP.

France also reported damage to its own embassy and the German one, but there was no information on possible casualties. Bulgaria said its mission had been damaged and its staff evacuated.

BBC journalists injured

The BBC's Afghan driver was killed and four of its journalists were injured in the explosion, the British broadcaster said.

“It is with great sadness that the BBC can confirm the death of BBC Afghan driver Mohammed Nazir following the vehicle bomb in Kabul earlier today, as he was driving journalist colleagues to the office,” the BBC World Service said in a statement.

“Four BBC journalists were also injured and were treated in hospital. Their injuries are not thought to be life threatening,” the statement said.

“Mohammed Nazir worked as a driver for the BBC Afghan Service for more than four years and was a popular colleague. He was in his late thirties and he leaves a young family,” it said.

Pentagon chief Jim Mattis has warned of “another tough year” for both foreign troops and local forces in Afghanistan.

Afghan troops are backed by US and Nato forces, and the Pentagon has reportedly asked the White House to send thousands more soldiers to break the deadlock in the battle against the Taliban.

US troops in Afghanistan number about 8,400 now, and there are another 5,000 from Nato allies. They mainly serve in an advisory capacity — a far cry from the US presence of more than 100,000 six years ago.

Wednesday's blast was the latest in a long line of attacks in Kabul. The province surrounding the capital had the highest number of casualties in the first three months of 2017 due to multiple attacks in the city, with civilians bearing the brunt of the violence.