HELWAN, Egypt (AP) _ Suspected Muslim extremists threw dynamite and fired automatic weapons at side-by-side movie houses, killing a policeman and injuring at least six other people, witnesses said today.

The attack came amid reports, so far unconfirmed by the government, that 1,200 suspected militants have been arrested throughout Egypt in the past week. Islamic extremists have waged a violent campaign for nearly two years to unseat Egypt's largely secular government.

The attack late Thursday on the theaters in Helwan, about 15 miles south of Cairo, took place just minutes after a film ended, but most of the audience had already left.

People screamed and ran for cover as the men attacked, four of them with automatic weapons, said Ali Taha Ali, who runs a projector. Two of the men threw sticks of dynamite, one at each theater before escaping by car.

A policeman was killed, the Interior Ministry said.

''All the glass in front of the theaters and in the ticket booth was shattered,'' another theater worker, Iman Taher, said.

Interior Minister Hassan el-Alfy, injured by Muslim extremists in an August bombing, visited the victims at Helwan General Hospital.

''Firing randomly in this cowardly way shows that these groups have reached a level of despair after the strong campaign by the police during the past few days,'' he said in a statement.

Many of those arrested the past week were reported to belong to the extremist al-Gamaa al-Islamiya, or Islamic Group. More than 240 people have been killed, including militants shot by police, during the campaign.

On Wednesday, police announced they had arrested 15 men suspected of membership in the outlawed Jihad, a revival of the group that killed President Anwar Sadat in 1981. All allegedly trained in Afghanistan and were charged with plotting attacks against government ministers.

Prime Minister Atef Sidki narrowly escaped an assassination attempt last month, a car-bomb attack that killed a 12-year-old girl and wounded 21 people. Jihad claimed responsibility.