NEW YORK (AP) _ The killings of five cab drivers in the Bronx, including three who may have been victims of the same robber, have terrorized hundreds of drivers who are sacrificing profits for daytime driving.

At the Seaman Car Service, employer of the latest victim, black flags flew Monday from the antennas of cabs, and drivers held a memorial procession.

At the Flash Car Service Co. in the Bronx, only 15 of the 80 drivers who normally work Sunday nights showed up for work, said dispatcher Pablo Feliciano.

''Most of them are switching to the days,'' Feliciano said. ''They're really disturbed about what's going on. Everybody's shaken up really badly.''

Drivers again vented their outrage later Monday when 400 to 500 cabs descended on a section of the Bronx and tied up traffic after hearing a false report on their radios that another driver had been shot, said Officer Fred Weiner.

With lights on, the cabs parked in the street and blocked traffic from 3 p.m. to 5 p.m., said Weiner, a police spokesman.

''A canvass of the car service companies did not turn up any drivers missing,'' Weiner said. ''They caused a major traffic jam over there.''

The latest killing Saturday and another three days earlier were dismissed by police as unrelated to the first three, but the slayings heightened fears in an area where cab drivers haven't felt safe for decades.

Officer James Terretta, part of a task force of about 30 officers investigating the slayings, said police do not have a suspect in any of the killings but are receiving many tips.

Mayor David Dinkins has offered a $10,000 reward for information leading to the killer or killers.

The terror spree began March 7 with the death of Acton Jones, 37. On March 14, 43-year-old Eliot Whitaker was killed, and on April 9, Paul Burghard, 25, was fatally shot.

In each shooting, a man phoned a car service requesting a cab, then killed the drivers with a shot to the head from a .22-caliber gun and robbed them.

Last Wednesday, Dennis Forbes, 41, the driver of an unlicensed cab, was shot in the head and killed before he had a chance to use a .25-caliber pistol police said he kept on the seat next to him.

Late Saturday, Rafael Montes De Oca, 38, of the Seaman Car Service was shot in the head and killed after he went to pick up a regular customer.

''The first three are connected and the last two are not,'' said Officer Ralph St. Just, a police spokesman. He said investigators refused to explain why.

In New York City, there are four basic types of taxicabs. Yellow cabs, also known as medallion cabs, roam the streets of the borough of Manhattan and airports, picking up passengers at random.

Car services, or so-called livery cars, generally operate outside Manhattan and are dispatched in response to customer calls. ''Black cars'' are used almost exclusively by corporate clients who arrange their pickups. Then there are thousands of unlicensed cabs which ply the streets.

The number of car services grew in the 1960s and 1970s when yellow cab drivers began avoiding the outer boroughs where they felt less safe and where there generally was no customer to return with to Manhattan.

Cars are dispatched from 120 bases in the Bronx but some companies have lost up to 80 percent of their drivers at night because of fear caused by the deaths, said Tony Carter, a spokesman for the Taxi and Limousine Commission, which licenses cabs in the city.

Customers calling cabs in the Bronx now wait an hour or more for a car that used to be at their doorstep in 10 to 20 minutes, he said.

Last year, 32 cab drivers were killed, about half of them in the Bronx, said Officer Kim Royster, a police spokeswoman. Citywide, 3,032 cabbies were robbed last year.

There are 11,787 yellow cabs, 35,000 livery cabs and up to 20,000 unlicensed cabs in the city.

Of the 1989 deaths, 28 were livery drivers and four were medallion drivers, the spokeswoman said.