BBC correspondent Greg Barrow reports from Pretoria: "orders from the president"

The former Law and Order minister, Adriaan Vlok, told the Truth and Reconciliation Commission that he received orders from Mr Botha to engineer the bombing.

Mr Vlok said the government believed the headquarters was being used as a refuge and weapons store for anti-apartheid activists.

The Truth and Reconciliation Commission is considering amnesty appeals from Mr Vlok and more than 30 senior police officers in relation to the high profile bombing campaign of the 1980s, which was carried out by the state security services.

Vlok: appealing for amnesty

Correspondents say Mr Vlok's evidence is the most direct evidence against Mr Botha, who is facing contempt charges for refusing to testify before the commission.

Mr Vlok and the policemen may receive immunity from prosecution if they reveal all they know about crimes committed to try to prop up white-minority rule during the apartheid era.

According to Mr Vlok's submission, Mr Botha told him the building, Khotso House, must be destroyed but all efforts should be made to avoid loss of life.

Mr Vlok said: "Mr Botha gave the instruction that the current situation should not be allowed to continue.

"It was totally unacceptable that the ANC had a safe house in Khotso House where terrorists could hide unhindered...without something being done about it."

Scores injured

Mr Vlok said the president had given no specific instructions on how the building should be destroyed, but after the bombing Mr Botha had congratulated him and the police.

The bombing was carried out without fatalities, but scores of people were injured by flying glass and falling masonry.

Mr Vlok said that while he personally believed that apartheid was wrong and morally indefensible, it represented a better alternative to Communism.

He praised the work of the Truth and Reconciliation Commission and said it was time for people like to him who had helped to "plant the tree of apartheid" to accept the moral and political responsibility for its fruits.

Mr Vlok is the only former government minister to have applied for amnesty as part of the commission's investigations into political crimes committed during the apartheid era.

Bombings marked changed tactics

The bombing campaign also included several cinemas which were showing Cry Freedom, the film that depicted the life of the late black consciousness leader Steve Biko.

BBC correspondents say the campaign marked a sinister turn in the government's total onslaught policy against anti-apartheid activists.

Suddenly, action by the security forces moved from individuals to whole groups of people seen as a potential threat to the apartheid government.

Who knew what?

The commission is trying to establish the extent to which government ministers were aware of the bombing campaign.

Mr Botha is awaiting the outcome of his trial on a contempt charge brought after he refused to comply with summonses to appear before the commission.