JOHANNESBURG, SEPT. 15 -- The South African police today announced a tough, new campaign, code-named "Operation Iron Fist," to crack down on the continuing wave of black township violence that has claimed more than 700 lives in the past six weeks.

Maj. Gen. Gerrit Erasmus, police commissioner for the Johannesburg region where most of the violence has occurred, said measures would include use of curfews and roadblocks; patrolling of townships in armored police vehicles mounted with machine guns, and marking of crowds with colored substances dropped from helicopters.

The measures, he said, would also include the fencing of migrant workers' hostels and squatter settlements with razor wire, and efforts to prohibit anyone from entering or leaving a migrant hostel without a search for weapons at designated gaps in the wire cordons.

African National Congress leader Nelson Mandela strongly condemned the measures, saying the use of more violent methods in the troubled townships could only result in more deaths.

"Operation Iron Fist" is coming into force three weeks after the government declared a limited state of emergency in the Johannesburg region in an effort to curb the violence. Instead, the violence has continued to escalate.

Erasmus used tough language in making the announcement at a news conference, saying the police would "react very strongly" against those perpetrating "this senseless, intolerable violence."

Attackers hiding in crowds would be "taken out," he warned.

Asked about the machine guns, Erasmus said they would only be used against individuals and not fired into crowds.

"They attack us with AK-47 automatic rifles and other weapons. Shotguns against an AK are no good. The machine guns are there to protect my people," Erasmus said.

The police commissioner suggested that Mandela had agreed to the measures Friday at a meeting with President Frederik W. de Klerk.

"Mr. Mandela wants an iron fist -- we'll give him an iron fist," Erasmus said.

But a visibly angry Mandela called a news conference at his Soweto home soon afterward to deny that he had agreed to the measures, which he said de Klerk had not shown him.

"Some of the measures leave much to be desired and will create more problems," he said, adding that they seemed designed more to address white fears than the situation facing blacks.

Mandela was particularly critical of Erasmus's threat to "take out" attackers in crowds, saying this gave police "a license to kill our people indiscriminately."

He also criticized the plan to surround the troubled hostels and squatter settlements with razor wire, saying this would make it impossible for people to escape if the premises were attacked and set on fire.

"This is a reckless measure that would never be used on whites in a similar situation," he said.

Mandela argued that the measures failed to address the real problem, which he said was the action of elements in the security forces who were promoting the township violence to destabilize the negotiation process between the government and the ANC.

Mandela told reporters Friday after meeting with de Klerk that the president now accepted that the violence was being manipulated by a "hidden hand," or "third force," and that de Klerk would announce comprehensive measures Monday to end this. Mandela would not speculate on why the police announced the measures two days early.

In a speech in the Cape Province town of Middelburg today, de Klerk confirmed that he was convinced that the township violence was being "used and misused" by an unknown third force.

"Who they are must be ascertained. It is not impossible that they come from within the ranks of the fighting factions themselves. Alternatively, they may come from sources as yet unknown to us," de Klerk said.

However, the president added that the existence of such a third force did not mean that the root causes of the fighting between black groups could be overlooked and that black leaders did not have a political responsibility to urge their followers to make peace.