Graeme Smith's South Africa will miss the ICC Trophy in Pakistan
South Africa will not take part in the ICC Champions Trophy in Pakistan in September because of security fears.
Cricket South Africa (CSA) made the decision, despite assurances from the International Cricket Council, after a meeting with the ICC in Johannesburg.
CSA studied security in Pakistan and plans for the event, along with reports from the South African government.
England, Australia and New Zealand have also expressed doubts about taking part in the tournament from 12-28 September.
"Four countries have now decided against coming to Pakistan," Pakistan Cricket Board chief operating officer Shafqat Naghmi told Reuters news agency.
"I probably shouldn't bracket the other three with South Africa as they have yet to announce their decisions but from what we are hearing they will probably do the same."
The ICC executive board will meet on Sunday to make a final decision on the fate of the tournament.
CSA president advocate Norman Arendse said: "We urge the ICC to reschedule the tournament as soon as possible."
Sri Lanka are the designated back-up hosts, and further talks about a possible shift in venue are to be held by the ICC before this weekend's meeting.
However, the Pakistan Cricket Board has said it will not participate in the Champions Trophy if the tournament is moved to another country, while the Board of Control for Cricket in India has said it supports Pakistan hosting the event.
Former Pakistan captain Javed Miandad said the two suicide bomb attacks which killed 67 people on Thursday had sent all the wrong messages to teams already reluctant to play in Pakistan because of security concerns.
"These attacks could not have come at a worse time and I think other teams like Australia, New Zealand and England will also now take South Africa's line," he said.
"Pakistan should now try to ensure they are not deprived of hosting rights," he said.
Haroon Lorgat, the ICC's chief executive, has previously ruled out a relocation.
But Naghmi attacked South Africa's decision and admitted it would damage the event.
He said: "We are deeply disappointed and when a decision was to be made on Sunday we think South Africa made a hasty choice.
"Now it's up to the ICC to take a decision which they would take on Sunday but I would say that South Africa's refusal will badly hurt the event. We will still do our best to save the event and host it on schedule.
"We made the best security arrangements for South Africa when they toured us last year and it was only at the end that they did not want to play in Karachi so we relocated the match to Multan."
South African Cricketers' Association CEO Tony Irish said: "This was a difficult decision but the right one.
"There is nothing more important than the safety of our national team."
The ICC task force has travelled to Australia, New Zealand and England in recent weeks to discuss security issues with the national cricketing bodies.