A third massive explosion jolted central Kabul late Monday, hours after a Taliban double bombing killed at least 24 people and left 91 others wounded, in another day of carnage in the Afghan capital.

Confusion reigned over the location of the third blast, which was followed by a brief spell of gunfire, with the interior ministry saying the target was unclear but local media suggested a guest house had come under attack.

It shook the capital just hours after high-level officials, including an army general, were killed in the twin blasts near the defence ministry, as the Taliban ramp up their nationwide offensive against the US-backed government.

A suicide bomber struck the area just minutes after the first explosion, in an assault apparently aimed at inflicting mass casualties as officials left the ministry after work.

"The first explosion occurred on a bridge near the defence ministry. The second struck just as soldiers, policemen and civilians hurried to help the victims," defence ministry spokesman Mohammad Radmanish told AFP.

Ambulances rushed to the scene, littered with disfigured bodies and charred debris. But there were so many bodies that some had to be taken to hospitals in car boots and the back of police pickup trucks.

Firemen, meanwhile, raced to retrieve some bodies thrown into the Kabul River by the intensity of the first blast on the bridge.

Health ministry spokesman Waheed Majroh said the attack left 24 people dead and 91 others wounded, some of them seriously, adding the casualties could rise still further.

The Italian-run Emergency Hospital in Kabul, which was overwhelmed with wounded patients, tweeted that four people died on arrival.

There was no immediate word on any casualties from the third explosion.

The violence highlights the deteriorating security situation in the country, which has taken a heavy toll on civilians.

- Rising insecurity -
"The enemies of Afghanistan have lost their ability to fight the security and defence forces of the country," President Ashraf Ghani said, condemning the carnage.

"That is why they are attacking highways, cities, mosques, schools and common people."

Taliban spokesman Zabihullah Mujahid said on Twitter that the defence ministry was the object of the first attack, while police were targeted in the second.

The violence comes more than a week after 16 people were killed when militants stormed the American University in Kabul, in a nearly 10-hour raid that prompted anguished pleas for help from trapped students.

Explosions and gunfire rocked the campus in that attack, which came just weeks after two university professors -- an American and an Australian -- were kidnapped at gunpoint near the school.

Their whereabouts are still unknown and no group so far has publicly claimed responsibility for the abductions.

The uptick in violence in the capital comes as the Taliban escalate nationwide attacks, underscoring the worsening security situation since NATO forces ended their combat mission at the end of 2014.

Afghan forces backed by US troops are seeking to head off a potential Taliban takeover of Lashkar Gah, the capital of the southern opium-rich province of Helmand.

The Taliban have also closed in on Kunduz -- the northern city they briefly seized last year in their biggest military victory since the 2001 US invasion -- leaving Afghan forces stretched on multiple fronts.