At the Islamic Center, veiled women and men in flowing robes knelt on the plush Persian carpet and prayed to Allah as the sunlight bounced off the blue and white mosaic walls of the mosque, creating a guazy, otherworld atmosphere.

On the Mall two miles away, another group of Islamic followers, members of the largely black American Muslim Mission, spread tiny rugs and even Army blankets and tablecloths on the grass and conducted the same prayers in the open air. Afterward, they ate barbecued chicken, potato salad and watermelon and listened to jazz and Stevie Wonder songs against a backdrop of the U.S. Capitol.

Though they differed greatly in style, both groups, the Americans on the Mall and the more orthodox, international group at the Islamic Center at 2551 Massachusetts Ave. NW, were celebrating the same religious event yesterday -- the breaking of the fast of Ramadan, the traditional month-long period of atonement and abstinence from food during daylight hours. It is a holy day equal in significance to Christmas or Easter for Christians.

Mostafa Abulghaith, a spokesman for the Islamic Center, estimed there are up to 60,000 followers of Islam in the Washington area. A spokesman for the American Muslim Mission, formerly called the Black Muslims, said about 320 local Muslims regularly attend weekly services at the mission's place of worship, 1519 New Jersy Ave. NW.

Despite the external differences, the message delivered to both groups from their leaders was basically the same: they must never surrender their religious beliefs and practices just to blend in with society.

For example, Abdullah Abdur-Rahman, 28, a Washington native who was at the mosque yesterday, said he wears a three-piece suit to work and is the most successful salesman of office furniture in his company. But he follows the special Islamic diet, prays the required three times a day facing the East, and at home, he wears the traditional kufi, or men's skull cap. In public, his wife is completely covered by clothing except for her eyes. He is studying Arabic and hopes to move eventually to an Arab country.

Betty Muhammad, a member of the American Muslim Mission on the Mall yesterday, wears less formal, loose fitting clothes and only a scarf to cover her hair. She refuses to walk behind her husband in the street like many orthodox Moslems. She does not much care for the formality of the services at the Islamic Center but says her faith in Islam is nonetheless a part of her day-to-day life.

In her Silver Spring neighborhood she has angered neighbors because she calls the police when she thinks some of the neighborhood children are riding stolen bikes or when some of the teen-agers begin fighting in the streets.

"People don't seem to mind much that I don't dress exactly like them and don't hang around with them. But they do mind if I insist the law be enforced. The hardest problem I have is in upholding my moral code," she said.

Some of the Moslems at the Islamic Center said they thought the American Muslims had introduced too many "innovations" to the faith. But said Taalib Abdul Samad, one of the Mission's Washington leaders, "Being American, we have a distinct identity. Our Islam allows for differences in culture but not in the practice of the faith."