Declaring that the nation's streets "are becoming a combat zone," police urged Congress on Friday to ban assault rifles like the one used to kill five children last month on a California playground.

"The police of America are pleading with you - my guys are pleading with you," Los Angeles Police Chief Daryl F. Gates told a Senate Judiciary subcommittee as it opened hearings on assault rifles.The session was designed to spotlight a bill introduced by Sen. Howard M. Metzenbaum, D-Ohio, that would ban the sale of AK-47s, Uzis and other military-style, semiautomatic rifles as well as sinister-looking, round-drummed shotguns that fire 12 blasts in three seconds.

In the Jan. 17 incident, a gunman opened fire with an AK-47 on 400 children on the playground outside Cleveland Elementary School in Stockton, Calif. Five children died and 29 were injured as well as one teacher.

Hush fell on the hearing as Lori Mackey, a teacher at the Stockton school, told how she and her pupils huddled on their classroom floor as shots crackled across the schoolyard and the shadow of the gunman, Patrick Edward Purdy, crossed back and forth across their window.

"We hoped that he would not notice that we were there and that he would maybe think that we were at recess, too," she said.

Since then, she said nightmares and fear of strangers have plagued her pupils and she has become distrustful and winces at unexpected sounds.

The AK-47 is a semiautomatic adaptation of the Soviet-designed rifle that has been the staple of Communist infantrymen from Vietnam to Afghanistan.

Gun groups are fighting the bill on grounds that it would outlaw not only so-called assault rifles but traditional wooden-stocked hunting rifles as well. In fact, there is no functional difference between the two, testified Edward Conroy, acting deputy associate director for law enforcement of the Bureau of Alcohol, Tobacco and Firearms.

The outspoken Gates, however, who claims authorship of the SWAT team concept, brushed aside the suggestion that legislation banning assault weapons would also prevent hunters from keeping their semiautomatic rifles.

"It seems to me that we're smart enough to do it," Gates said. He said lawmen can tell the difference. "I can tell you because I've had two police officers killed with assault weapons."

"Gang members love these weapons because in their drive-by shootings they don't have to be marksmen, they don't have to be sportsmen, all they have to do is spray," the chief said. He added that he is getting "pretty fed up with handing out flags to widows and little kids."

Metzenbaum told the committee that the California episode showed that the AK-47 was not meant for use "in a duck blind."

Also on hand were representatives of some of the nation's gun-owner groups, who argued that firearms were not the problem.

The Stockton incident "reflects a breakdown in the criminal justice system," said John M. Snyder, public affairs director of the Washington-based Citizens Committee to Keep and Bear Arms. He noted Purdy's previously misdemeanor arrest record and called on police to crack down on criminals and keep guns out of their hands.

National Rifle Association lobbyist James Jay Baker said that Metzenbaum's bill conflicted with the 2nd Amendment to the Constitution, guaranteeing citizens the right to keep and bear arms.