"We have talked to the (South African ambassador) in Islamabad and he too is very disappointed because he gave a positive assesment a few days back."
The United Cricket Board of South Africa (UCBSA) called off the tour only two days after giving it the green light and just 24 hours before the team was due to travel to the Islamic republic.
UCBSA president Ray Mali said security in Pakistan had deteriorated to an unacceptable level.
"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," Mali said.
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 14 people.
Cricket-mad Pakistan is desperate to bring international cricket back to its grounds after a 15 month drought.
"They have shocked us by calling off the tour. It's uncalled for and disappointing," PCB's chief executive Ramiz Raja told AFP.
Pakistan stands to lose 3.5 million dollars in sponsorship and television rights from the tour's cancellation, the PCB said.
The South Africans had given the go-ahead for the tour on Thursday, after dispatching its own delegation to Pakistan to assess venues considered risky in commercial capital Karachi and the northwest border city Peshawar.
"Why did we go through the exercise of giving security drills to their delegation?" Raja fumed.
The South African team was to arrive in Karachi Monday and had scheduled a warm-up match on Wednesday ahead of the first of three one-day matches on Friday, both in the commerical port city.
Pakistan had guaranteed state-level security for the team.
The PCB has offered to rescheduled the tour to start one week later and to change venues, spokesman Samiul Hasan said.
"We ... have offered them to change fixtures in Karachi and Peshawar and delay the start to tour by a week. We hope something positive will come out," Hasan told reporters.
The cancellation came in response to an explosion on the 10th floor of an empty commercial office block on Friday night in downtown Karachi.
No-one was injured or killed in the blast, and police ruled out terrorism, linking the blast instead to a commercial dispute involving the 12-storey Kawish Crown Plaza on the main road linking the international airport to the city center.
Bangladesh has led the return of foreign cricket to the terror-hit Islamic republic, playing three Tests and four out of five one-day matches without any security disturbance.
Raja said he was furious that Pakistan's successful hosting of Bangladesh, who wrap up their tour in Karachi on Sunday, meant nothing.
"We are hosting Bangladesh, aren't they human beings?" he said.
Both South African and Pakistani cricket would suffer, he warned.
"Their decision means that even cricket should not be played in South Africa where there are so many dangers.
"People in Pakistan are so passionate about cricket and it's a great deprival for them, having not seen cricket for 15 months and now being deprived of watching good cricket against South Africa."
New Zealand, which led the exodus of foreign cricketers, is scheduled to return to Pakistan on the heels of the South Africans in November.
Raja said that tour could be thrown into doubt by the South African cancellation.
"It could have serious implications on the New Zealand tour," he said.