Media playback is unsupported on your device Media caption Officials say dozens were killed or wounded in the attacks

Security has been stepped up in the Afghan capital after a series of bomb attacks killed more than 50 people.

Eleven people, including a Nato soldier and eight contractors, were killed in an attack on a base in Kabul.

On Friday, at least 25 people died in a suicide bombing at a police academy and a truck bomb killed 15.

The UN said the attacks were likely to be the product of a Taliban power struggle following the death of its leader Mullah Omar.

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

President Ashraf Ghani is due to hold a meeting of the National Security Council on Saturday to discuss the worsening situation and Afghan soldiers have been deployed across the capital to boost security.

Image copyright Reuters Image caption Afghan soldiers have been deployed alongside police at checkpoints in Kabul

Image copyright Reuters Image caption Hundreds of civilians were wounded in the multiple attacks on Friday

Image copyright AFP Image caption Peace talks between the government and the Taliban were suspended last week

The first attack came in the early hours of Friday morning, when a truck packed with explosives was detonated near an army base in the Shah Shahid area, killing 15 civilians.

Later on Friday, a suicide bomber dressed in a police uniform blew himself up near the city's police academy, killing at least 25 recruits.

A short while later, gunmen attacked Camp Integrity, a Nato base that houses US special forces near Kabul's international airport.

The Taliban said it was behind the attack on the police academy but has made no comment about the two other attacks.

'Succession battle'

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

"We suspect the upsurge in violence may be triggered by the succession battle within the Taliban," he told the BBC.

Last Monday, the Taliban released a video in which they showed members of the group pledging allegiance to the new leader, Mullah Akhtar Mansour.

But analysts suggest there has been infighting within the group between supporters and opponents of Mansour.

Such infighting threatens to kill off a tentative peace process that was suspended last week after the announcement of Mullah Omar's death.

President Ghani insisted the government was still committed to peace but said it "will respond to these sort of terrorist attacks with force and power".