CAP-HAITIEN, Haiti (AP) _ Lt. Shane Thomko watched as the slender, smiling Haitian military policeman strutted by, the baton he had just beaten a woman with stuck in the back of his trousers.

''These people are happy we're here because that is going to stop,'' said Thomko of Quincy, Ill.

The Marines landed at Cap-Haitien on the northern coast Tuesday in a picture perfect air-sea landing at Haiti's second largest city.

The movement of 1,900 Marines from ship to land went without a threat to any American life.

Haitian police cooperated as Marines secured the airfield and port and then moved tentatively into town.

But as they stood at their concertina-wire barriers, they became aware of the problems they will face in the days ahead.

Haitian soldiers strolled by, guns slung over their shoulders. Police pushed back curious and happy crowds, occasionally using fists and sticks.

One man who greeted the Marines, Jean Claude Charles, tore at his pants to show the purpling bullet wound in his thigh.

''The police shot me for no reason,'' he said. '' I was with people and I was happy that the Americans were going to come and they shot me.''

The police violence against civilians dismayed some of the Marines.

''All you gotta do is look at these people and see that they want to work and raise their families,'' said Lance Corp. Rudy Bueno of New York City. ''At this point, we're really all they were hoping for.''

The Marines came ashore at 8 a.m. with an amphibious landing at the port and a helicopter landing at the city's small airport. At each location, their arrival was met by cheering crowds, shouting ''Merci Beaucoup 3/8'' and ''Liberte 3/8''

At the edge of the airfield, a group of Haitian men waving an American flag ran along the defensive perimeter set up by Marine gunners.

''Everything's been great. When we first got here we thought we heard a shot and everybody hit the deck. But there was nothing else,'' Lance Corp. James Rayburn of Findlay, Ohio, said as he sat with his sniper unit in the shade of a long-ago wrecked plane.

In town it was the same. Crowds formed along side streets and on rooftops applauding the U.S. troops. They followed a group of Americans, singing their happiness at the anticipated return of democracy and exiled President Jean- Bertrand Aristide.

But there were occasions of violence as Haitian authorities sought to control the crowd.

The woman beaten by a Haitian policeman was treated by a corpsman for a bloody face.

At one point Tuesday morning, a truckload of plainclothes men carrying assault rifles approached the perimeter of the airport. They stopped, looked around, and before leaving told the guards at the barrier that they were not there to fight. The same group was seen several times during the day.

Marine Lt. Col. Steve Hartly, commander of one of the two task forces that landed Tuesday, said under the rules of engagement his men could only step in when murder or rape was involved.

''We have no authority to detain any Haitian military or police,'' he said.

Hartly also said there was no plan to disarm any Haitian forces. This made many of the Marines jittery as the long day turned toward dusk.

''A Navy interpreter talked to some of the people and then later told me not to trust them,' said Lance Corp. Thomas Goodman of Knoxville, Tenn. ''He said they don't want us here. He said to watch your back tonight.''

Hartly was to meet later with the local Haitian commander, Col. Claudel Josephat, to discuss coordination between the two forces.

Back at the airport, Herve Lebarbe, a Canadian resident of Haiti, watched as helicopter after helicopter of Marines came ashore.

''This is a good time for the people, they were expecting this for a long time,'' he said. ''But I wonder if it will last. Happiness is the first day. Reality comes later.''