Several people have been arrested in the Afghan capital, Kabul, after plans for an apparent mass suicide attack were foiled.
Intelligence officials have told the BBC that 11 suicide jackets were seized in the ministry of defence.
They say the attacks would have caused significant loss of life if they had gone ahead.
Some of those arrested are reported to be soldiers in the Afghan National Army.
The jackets were seized on Monday afternoon from three separate rooms around a ministry car park, less than a kilometre from the presidential palace.
It appears they were intended to be detonated on buses transporting staff to and from work.
The soldiers are being questioned as to how the jackets ended up in the rooms which they were supposed to be guarding.
The BBC's Bilal Sarwary in Kabul says the problem of attacks by rogue soldiers and Taliban infiltrators has plagued the Afghan police and army for several years.
The arrests came as people wearing the uniforms of Afghan security forces killed one US and two British soldiers in separate incidents, in Paktika province and Lashkar Gah respectively.
Attacks on US and Nato forces have increased since the burning of Korans by US troops in February and the murder of several Afghan civilians by a US staff sergeant on 11 March.
The last Nato combat forces are due to withdraw from the country by 2014. Meanwhile efforts are being made to build up the Afghan security forces and negotiate with the Taliban.
The Taliban pulled out of the talks, which were started last year, following the 11 March killings, accusing the US of being "erratic and vague" in its dealings with them.