Two men wearing gas masks tossed two canisters of smoke and tear gas into a Capitol Hill bar for homosexuals early yesterday morning, sending 50 coughing and gagging patrons scrambling outside, D.C. police reported.

Employes and patrons of Equus said that the assailants appeared to be U.S. marines. The bar is near 7th Street and Pennsylvania Avenue SE, a few blocks from the Marine Barracks at 8th and I.

Last August, a group of about two dozen marines, some of them apparently drunk, charged into the bar, assaulted one of its owners and broke windows.

The bar employes said the men who entered the bar Friday night carried military equipment and had close-cropped hair.

Ric Holloway, a co-oner of the bar, and several of his employes gave this account of the incident:

Two men entered the bar through the back door, each carring a canister. One of the men threw a canister against the wall, filling the bar with smoke, while the other man threw another canister (containing tear gas) on the ground. Both men fled through the back door, while bar patrons began coughing and groping toward the front door.

Holloway said he was in the front of hte bar talking to patrons when he saw sparks caused by one of the canisters. "It looked like an electrical explosion," said Holloway. He grabbed the fire extinguisher, saw the canister, and then ordered patrons out of the bar, he said.

Jim Chambers, a waiter, said he was standing by the pool table in the rear of the bar when he heard the back door open. Then the heard something hit a wall, he said.

"I saw sparks and then I saw the canister on the floor," Chambers said. "I kicked it back but there was a mass of smoke coming up. I told everyone to go to the front door.

"It was so confusing. People were trying to see what was going on. Then their eyes started burning and their throats started gagging. They all came out choking coughing. This whole sidewalk in front of the door was nothing but people lying, kneeling and coughing."

D.C. police, who do not have any suspects yet, said there was no certainty that the men were marines. "Just because people say they look like marines doesn't mean they were marines," said D.C. police officer Charles Moncrefe.

Cpl. Gil Robinson, a spokesman for the Marine Barracks where 800 marines are stationed, said there was no proof that marines were responsible for the tear gas incident.

"As far as I know, there's no evidence showing that there were marines involved," said Robinson. "It's sort of tough to identify people with gas masks on."

The marines do not store tear gas or smoke canisters at the base, according to Robinson, but about 50 marines possess gas masks. Such canisters can be purchased by anyone at military surplus and supply stores, he said.

Yesterday's incident stirred anew the controversy between members of the city's gay community and the marines. During the past several years, marines and gays have had a tense and sometimes hostile relationship.

Marines complain that gays try to pick them up for dates, while gays complain that marines spit on and break the windows of gay bars. "They feel threatened by us because their own masculine image is not secure," Doug Wright, editor of Out, a magazine for homosexuals, said yesterday.

About a dozen persons stood outside the bar yesterday while large fans tried to clear the air inside. Several of those outside said they were angered by the incident.

"This is getting real serious," said Holloway. "It makes you wonder what the hell will happen next. I expect someone to come through the door with a gun."