The doors of New Samaritan Baptist Church on Maryland Avenue NE near Stanton Park used to be kept open all the time, but now they are locked. At the Brookland Parish Episcopal Church at 16th and Irving streets NE, groups now notify the police when they meet at the church and then draw the blinds so no one will know there are people inside.

Both are among eight Washington churches that have been victimized by armed robbers since November, with all but one of the robberies taking place on weeknights when Bible classes or other church groups were meeting, according to D. C. police.

The robberies have been reported at churches in the Northeast and Southeast sections of the city. Three similar incidents are being investigated in Prince George's County. District police said they believe one man may be responsible for all or most of the robberies.

Police describe the robberies as unusual although there have been rashes of burglaries at churches.

Only one of the recent robberies took place on a Sunday. Nearly all were committed between 8 p.m. and 10 p.m., when Bible classes or choir practices were in session.

In the case of New Samaritan, at around 9 p. m. on Jan. 8 the leader of a youth organization was checking the doors in the basement of the church, the Rev. Robert Harrison said, when he was approached by an armed man, led into a classroom and robbed.

"These are paying times. Also serious times," said Harrison. "It's incredible."

Harrison said he has since "warned the congregation of the danger" and started locking the church doors. "For some reason we felt the church should be open for the convenience of the parishioners," Harrison said. "But it hasn't worked out. We're forced into being more cautious."

The first such robbery was reported Nov. 16, around 9 p.m., when a man entered the James Memorial Baptist Church, at 1723 3rd St. SE, and robbed three persons. On Nov. 20, an armed man entered the fellowship hall at Mt. Horeb Baptist Church, 2914 Bladensburg Rd. NE, and robbed eight persons attending a Bible class.

On Jan. 5, a man rang the bell outside Brookland Parish Episcopal and asked to see a priest. He drew a revolver and robbed 13 members of the church's men's organization, who were holding their monthly meeting. On Feb. 1, the most recent case, a man bearing a sawed-off shotgun robbed 21 persons attending a class at Plymouth Church, 5301 North Capitol St.

Lt. James R. Waybright of the police department's robbery squad said there is little to prevent such robberies because churches take few security precautions. But Waybright, a practicing Baptist, says he has faith that the man--or men--responsible will be caught.

"There's no doubt in my mind that eventually the Lord is going to put something down on these guys," Waybright said. "He may be working through our agency, but He's definitely going to get 'em sooner or later."

Police are offering a $1,000 reward for information leading to an arrest in the cases. illustration: Police are looking for this suspect in recent armed robberies in city churches.