"The decision has been taken with much regret. We know how much the tour means to the people of Pakistan and it is also a tour which we have been looking forward to. But the safety of our players is our primary concern," said United Cricket Board of South Africa (UCBSA) president Ray Mali.

Mali said the UCBSA and the Board of Directors of Cricket South Africa had no alternative but to call the tour off since the security situation in Pakistan had deteriorated to an unacceptable level, the SAPA news agency reported.

South Africa would have been the first Western team to tour Pakistan since May 2002, when New Zealand cut short their tour after a bomb outside their Karachi hotel killed 15 people.

The South African decision to pull out of the tour was taken after talks with UCBSA's safety and security consultants, the High Commissioner in Islamabad and international intelligence sources after the Karachi bomb blast.

Nobody was injured in the attack on a downtown office block.

"Cricket SA (Pty) Ltd also consulted with the South African government at the highest level before making its decision. Based on that information and our consultations, the Board decided that the team's departure to Karachi tomorrow would have constituted an unacceptable risk," a UCBSA statement said.

South Africa were due to leave for Pakistan on Sunday for the month-long tour which would have included three Tests and as many one-day internationals.

Last week, South Africa sent a three-man delegation to Karachi to carry out a security survey and returned to declare Thursday that the tour would go ahead.

But then came Friday's attack.

UCBSA commercial director Ian Smith, who led the delegation, said in Saturday's statement: "We have gone to great lengths to make sure the tour could go ahead, but the most recent developments have left us with no option."

The port city of Karachi was scheduled to host a Test match and two one-day games against the South Africans.

Pakistan were forced to play its "home" series against the West Indies and Australia at neutral venues last year due to security concerns.

The Pakistan government promised to provide adequate security to the South African team during its tour.

The UCBSA have offered to host the one-day International and Test series in South Africa, or alternatively at a neutral venue to be agreed by both parties.

Otherwise the tour could be postponed to a later date when the level of risk in Pakistan is acceptable, the body said.

The International Cricket Council has been informed of the UCBSA's decision.