JOHANNESBURG, DEC. 30 -- The government unveiled a broad new campaign today to crack down on South Africa's soaring crime rate, but opposition groups said they feared the effort is a cloak for a security crackdown on them.

Law and Order Minister Adriaan Vlok said in an interview on state-controlled television that the government would add 10,000 policemen to the national force of 75,000 by July as part of the new measures and increase border controls to stem an influx of automatic weapons. Other press reports said police would step up patrols, house-to-house searches, road checkpoints and other operations in the volatile black townships.

The influential Sunday Star newspaper said the crackdown could return South Africa to "a virtual state of emergency," referring to the declarations of martial law that led to the imprisonment without trial of about 40,000 political activists over five years.

Vlok denied the new campaign would suppress political activism, saying it was aimed at ordinary criminals threatening life and property in prosperous white suburbs as well as in sprawling black townships. Officials cited police statistics reporting 12,840 killings during the first 10 months of 1990, an increase of 25 percent over the same period last year, and similar jumps in other violent crimes, such as assault, rape and robbery.

"People have become numbed; life has become cheap," Police Commissioner Johan van der Merwe told reporters.

During the Christmas holiday week, 19 persons were killed in political violence and another dozen in attacks that appeared to have no political element. The incident that caused the greatest public indignation was the gang rape of six girls, aged 13 to 16, after they were abducted from a Salvation Army shelter in the black city of Soweto early Christmas Day.

Police were called but reportedly arrived long after the assailants, who also looted the shelter and wounded two adult guardians, had fled with the girls. A group of outraged citizens hunted down eight alleged assailants, members of a black street gang, and handed them over to authorities.

"People can't fold their arms and wait for the police to protect them against criminals," said Soweto Civic Association spokesman Kgabisi Masunkutu.

Vlok said the new campaign would seek to enlist such citizen participation against crime and correct the "misconception" that police were not interested in serving the black community. But critics contend the police force is so discredited in this divided society that it will take much more than numbers to restore public confidence.

In large areas of Soweto, few people venture out at night, and many keep their doors and windows locked even when they are home. "If you go to the police, you are considered a sellout," said a black business manager who lives in the up-scale Diepkloof neighborhood. "So we sit behind our bars and locked doors, and we cower."

"Obviously we're concerned about protecting people from crime, but we're also very concerned about the security element of this campaign," said Gill Marcus, spokeswoman for the African National Congress, the chief anti-apartheid movement here. "We're wondering if this is a way to get people to accept the suppression of political movements as well as the so-called criminals."

Political militants for years have targeted police for their role in suppressing dissent. Ninety-one policemen have died on duty this year -- 65 of them in politically related incidents, according to official statistics. The ANC has accused police of instigating or participating in a wave of black violence in townships.

President Frederik W. de Klerk pledged in August at a joint press conference with ANC Deputy President Nelson Mandela that policemen who violate the law would be punished. But Mandela said the government had failed to act on information the ANC had passed on.

The difficulty in separating "political action" from ordinary crime is illustrated by the widespread use of AK-47 automatic rifles in a recent spate of a dozen robberies here. Police say many of the weapons are being smuggled into the townships from neighboring Mozambique via Swaziland -- also the main smuggling route for arms used by ANC fighters during its now-suspended armed struggle against the government.