There was no immediate connection between the four robberies, which occurred in the Bayview and Mission districts, and in the Mission Terrace neighborhood, police said.
Police said a 28-year-old man was robbed at gunpoint of his cell phone and wallet by two youths in their late teens at 4:15 p.m. in the 1000 block of Oakdale Avenue.
At about 9:30 p.m., two men in their late 20s invited two other men over to their house but were then robbed at gunpoint of their phones and other property, police said. One of the suspects was later arrested.
Two other robberies occurred in the Mission District at 8:40 p.m. and just after 4 a.m., according to police.
In the first, a 36-year-old man was attacked by three men in the 800 block of Valencia Street and his wallet and cell phone were stolen.
At 4:10 a.m., a 38-year-old man was sitting on the sidewalk and working on his laptop in the 1600 block of 15th Street when a man and a woman in their 20s approached him, according to police.
The man grabbed the laptop, and when the victim followed and confronted him, he was hit on the head with an unknown metal object, police said. The victim was hospitalized with minor injuries, and the suspects escaped.