A suicide bomber killed dozens of cadets at a Kabul police academy and insurgents struck an area near a U.S. special forces base yesterday in a wave of attacks in the Afghan capital that began with a huge early morning truck bomb explosion.

A Kabul police official, speaking on the condition of anonymity because he was not authorized to brief the news media, said that at least 25 people were killed when four suicide attackers tried to enter the Kabul Police Academy compound shortly before 8 p.m., setting off explosives in an attempt to breach the wall.

The Afghan capital had been on alert since early on Friday, when a massive truck bomb exploded outside an Afghan army base in a residential area called Shah Shaheed, close to the centre of Kabul.

Explosions and gunfire also erupted when Camp Integrity, a US special forces base in Kabul, came under attack late Friday, killing nine people, including a North Atlantic Treaty Organisation service member.

The bombings are the first major attacks after Mullah Akhtar Mansour was named as the new Taliban chief last week, in an acrimonious power transition after the death of longtime leader Mullah Omar.

Friday’s death is only the third for coalition service members so far this year, as tens of thousands of troops were withdrawn last year, and the remaining forces have largely retreated into a handful of fortified bases around the country.

Since the U.S.-led invasion in 2001 that ousted the Taliban, Kabul always has been the target of insurgent attacks.

The Taliban took responsibility for the suicide attack on the police academy, and claimed that more than 50 police had been killed or injured.

The attacks, which happened within 24 hours of each other and injured hundreds, are the first major incidents since the Taliban confirmed last week that Mullah Omar died two years ago.

Thomas Ruttig of the Afghanistan Analysts Network said: “The hope of some people was that the death of Mullah Omar would put the Taliban in disarray and possibly weaken them, I think that was a little over optimistic”.

The statistics are a grim indicator of the expanding insurgency, with Afghan forces increasingly battling the militants on their own after NATO’s combat mission ended in December.

There appears to be no easing in the intensity of the fighting between the Taliban and Afghan forces, which has caused nearly 5,000 civilian casualties this year, according to a recent report by the United Nations.

Afghans gather at the site of a vehicle bomb attack in Kabul, Afghanistan, on Friday.

The number of casualties from yesterday’s attacks was expected to rise as details continued to emerge from the authorities. Many Afghans use only one name.

Nicholas Haysom, the head of the UN mission in Afghanistan, said the attacks were probably linked to the current power struggle within the Taleban.