Image caption The explosives were seized during a wave of insurgent attacks last week

Afghan security officials say they have foiled a huge attack in the capital Kabul, as they gave details of the seizure of 10 tonnes of explosives.

The explosives were found in a truck seized along with five militants in an operation last Sunday, a National Directorate of Security spokesman said.

The group was planning to attack crowded areas in the capital, he said.

He also gave reporters a video detailing plans for a separate attack on Vice-President Mohammed Khalili.

Describing the planned bomb attack on Kabul, the spokesman, Shafiqullah Tahiri, said the 10 tonnes of explosives were stuffed in 400 bags and hidden under piles of potatoes.

"If this amount of explosives had been used, it could have caused large-scale bloodshed," Mr Tahiri said.

He said three of the captured militants are Pakistani citizens, and two are Afghans.

'Confessions'

The five suspects had confessed that the planned attack was co-ordinated by two Taliban commanders with links to Pakistan's main intelligence organisation the Inter-Services Intelligence agency (ISI), according to the spokesman.

The arrests, which came during a wave of insurgent attacks around the country, was kept quiet at the time because of the ongoing security operation, he said.

Afghanistan has often accused the ISI of involvement in supporting anti-government insurgents in Afghanistan - an allegation strongly denied by Pakistan.

Last week, 51 people died in a wave of co-ordinated attacks by insurgents in Kabul and three other provinces.

The BBC's Bilal Sarwary says the security forces are under criticism for failing to anticipate the attacks, and are keen to show that they are making progress in their investigations.

In a separate operation, security forces detained a group of fighters - including suicide bombers belonging to the Pakistan-based Haqqani network - planning to assassinate Afghanistan's second Vice-President, Mohammed Khalili, Mr Tahiri said.

The Haqqani network is a mainly Afghan ethnic Pashto group operating out of the north-western Pakistani tribal areas, and is seen as linked to, but separate from, the Afghan Taliban.