Three D.C. police officers were shot last night, one critically, when gunfire erupted in Southwest Washington as an undercover drug purchase went bad, police said.

Police were seeking two men who fled from the shooting, which occurred about 8:30 p.m. at South Capitol Street and Martin Luther King Jr. Avenue, near Bolling Air Force Base. A third man was arrested immediately after the shooting by officers backing up the drug deal.

Two of the wounded officers were posing as narcotics dealers hoping to buy thousands of dollars worth of PCP at an abandoned gasoline station.

Instead, their sellers, apparently hoping to rob the undercover officers, immediately opened fire.

It was the third drug-related incident in less than a month in which D.C. officers have been shot and wounded while on duty. Six officers have been wounded in the incidents.

"We have had an awful lot of violence associated with drugs," said Police Chief Maurice T. Turner Jr., who called undercover drug purchases the most dangerous police operation.

One officer, identified as Troy Pumphrey, 25, a three-year member of the force, was in critical condition at Hadley Memorial Hospital after being hit in the chest, groin, shoulder and upper leg. He went into surgery after 9 p.m. and was still in surgery at 2 a.m., a police spokesman said.

Two other officers were taken to Greater Southeast Community Hospital with lesser injuries.

Police said one of the officers, identified as Gerald Awkard, 40, with 16 years on the force, was saved by a bulletproof vest after being shot in the back at close range.

He received only a severe bruise.

The third officer, Richard Watkins, 36, with 14 years on the force, was wounded in the leg. Greater Southeast officials declined to release the conditions of the two officers treated there.

The three officers are assigned to the narcotics unit.

Turner said the shootings were the climax of an extended undercover operation in which the officers "They just walked up to the car and opened fire."

-- Police Chief Maurice T. Turner Jr.

were to purchase "several thousand dollars" worth of the hallucinogen PCP.

Pumphrey and Awkard drove up to an arranged meeting spot at an Exxon gasoline station at 3900 Martin Luther King Jr. Ave. SW.

Moments after Awkard got out of the car, two men with whom they had been negotiating fired a shot at him point-blank, Turner said.

"It was a rip-off," Turner said, adding that police think the gunmen had planned to rob the officers instead of selling them the PCP.

Awkard, wearing the protective vest, fell after being struck. Pumphrey was hit four times. The third wounded officer, who had been sitting in a nearby unmarked car to provide backup, was shot as he rushed to help the officers making the purchase.

After an exchange of gunfire with other backup officers, one of the alleged gunmen raced across Martin Luther King Jr. Avenue, where he was arrested outside a National Bank of Washington branch.

The suspect was identified as Herbert Austin, 20, of 2912 2nd St. SE. A police spokesman said charges were pending in the case.

The second gunman fled east into a wooded area near the Anacostia Freeway.

Another man, who did not fire any shots but was believed to be an accomplice, also fled.

Aided by a helicopter, police concentrated their search in the woods near the freeway.

Naval security officers also conducted a search in the U.S. Naval Research Laboratory.

The search also spread into Bolling about 10:30 p.m., after Air Force officials told police a man matching the description of one of the gunmen was seen entering the Air Force base.

Turner said police knew the missing suspects' identities and were confident of arresting them.

The shootings were the latest in an epidemic of attacks against District officers.

Two officers were shot during a foot chase Nov. 21.

The gunman, who was carrying 25 packets of the potent cocaine derivative "crack," was shot to death after he was barricaded near a Northeast day care center.

On Dec. 1, an officer was shot and critically wounded while making an undercover drug purchase in a notorious outdoor Northeast drug market as part of Operation Clean Sweep.

The same officer had been shot at, but not wounded when the bullet hit his handcuffs, in a similar drug operation two nights earlier.

Police declined to say how many officers were backing up last night's undercover operation.

But Turner said there was "ample" support, adding, "They just walked up to the car and opened fire."