JERUSALEM (AP) _ The outlawed anti-Arab Kach group has formed an underground paramilitary force that masquerades as Israeli security agents in Arab villages, a member said Wednesday.

The Kach activist, who spoke on condition of anonymity, said members of the underground force drive cars usually associated with Israeli security forces to penetrate army roadblocks barring Israelis from Arab villages.

Once inside ''we lift the law off the ground,'' the activist said.

He said the patrols treated stone throwers in a way that would deter them from ever doing it again, but would not elaborate.

The daily Yedioth Ahronoth said the Kach members smash windows and slash tires in the Arab towns. The newspaper carried a photograph of a Kach member and a car like those usually driven by Israeli security forces.

Israel police spokesman Eric Ben-Ruby said police were looking into the reported Kach force.

''If laws are being broken, it will be dealt with accordingly,'' Ben-Ruby said.

The extremist Kach movement was outlawed and its leaders jailed after a Jewish settler shot and killed 29 Palestinians in a Hebron mosque in February.

The settler, U.S.-born Baruch Goldstein, was a member of Kach, which advocates expulsion of Arabs from all Israeli-held territory.

Since the massacre, even wearing a T-shirt with the movement's name is a crime in Israel. Kach members have sworn to continue their extremist activity under a new name.