BAGHDAD, Iraq — Masked gunmen rampaged through a district of Baghdad yesterday dragging people randomly from cars and killing those who were Sunnis.

In a day of violence that was severe even by the Iraqi capital’s bloody standards, at least 41 people were believed killed in attacks thought to have been in retaliation for the bombing of a Shiite mosque on Saturday night that killed at least two and injured nine.

The massacre started at around 10 a.m. as the armed men, who Sunnis claim were members of the fanatical militia loyal to Muqtada al-Sadr, the fundamentalist Shiite cleric, drove into the Jihad district in four cars.

They set up road blocks and demanded to see people’s identification cards to determine their sect before roaming through the area and killing those they thought were Sunni, police said.

Bodies were scattered throughout the neighborhood by the time Iraqi security forces arrived an hour later.

One shopkeeper, a Shiite, described how he saw the armed men pull four people from a car, blindfold them, and force them to stand to the side while five more people were ordered out of a minibus.

“After 10 minutes, the gunmen took the nine people to a place a few meters away from the market and opened fire on them,” he said. “When I heard the gunfire, I closed my supermarket and went home.”

The deputy prime minister, Salam al-Zubaie, described the attack as “a real and ugly massacre” and criticized the security forces for failing to maintain order. “There are officers who instead of being in charge should be questioned and referred to judicial authorities,” he said.

The cycle of sectarian attacks appeared to be worsening last night when security officials announced that at least 15 people were killed and 35 injured by two car bombs near a Shiite mosque in a Sunni district.

The attacks came as the Los Angeles Times published documents allegedly showing that Iraqi police officers have been party to abductions, murders, and the rape of prisoners.