Four armed street robberies were carried out within a few hours Sunday night and Monday morning in the Columbia Heights neighborhood of Northwest Washington. All seemed to follow a similar pattern, police said.

One victim was struck with a pistol and another was cut on the mouth. Three of the robberies occurred within about 15 minutes. In one case, $500 was taken.

In the first of the incidents, three robbers came up to two people in the 1400 block of Oak Street NW and demanded property. They got two iPhones, two wallets, a necklace and a pair of glasses, police said.

At some point, one robber drew a pistol and struck one victim in the head, causing a bruise behind the ear and a cut.

That robbery occurred about 9:50 p.m. Sunday.

The next incident, according to a police account, occurred about five minutes later, four or five blocks away, in the 3600 block of 14th Street NW.

Three robbers confronted their victim and asked for $1, authorities said. The person was punched and fell to the ground. One robber demanded that items be surrendered. At first, the victim refused. It was then that the robber drew a knife and cut the victim.

The robbers fled with a wallet, which contained the $500.

Within about five minutes, according to police, a third robbery was carried out, about a block away. In this robbery, the victim was approached in the 3400 block of Holmead Place NW, police said. Property was demanded; a pistol was shown, and the victim handed over a phone.

However, police said, the robbers wanted more. The robber with the gun began accompanying the victim toward his house. But as they walked, the sound of sirens put two of the robbers into flight. The third robber, who had the gun, continued to walk with the victim.

But as they walked, police said, the victim suddenly began to run. The robber ran after him. But the victim got into his apartment, and the robber ran away, police said.

A fourth robbery also appeared to follow the same pattern, although it occurred almost five hours later, the police said. It happened in the 1600 block of Irving Street NW, not far from the sites of the other incidents.

In that robbery, which occurred about 2:50 a.m. Monday, police said, the victim was entering the building where he lived. Two robbers followed. One grabbed the victim, and when he resisted, the robber drew a pistol. The second robber pulled out a knife. The victim was held at knifepoint as the first robber went through his pockets. The victim began to scream. The first robber took an iPhone charger from the victim’s pocket, and then both of te robbers ran.

Suspect lookout: two black males, 23-25 years old, slim build, medium complexion, wearing black masks and dark clothing, one armed with a black handgun and the other armed with a knife

Descriptions in all cases had similarities: All the robbers were described as black and in their 20s, with dark clothing. In each case, at least two of the robbers were said to be men. One victim said that of three robbers, one appeared to be female, and in another case the victim reported that the robbers wore masks.