Gunmen in northern Nigeria have killed seven people in attacks that resembled previous strikes by a feared Muslim sect, police said, though authorities said copycats may have been responsible for most of the killings.

   Monday’s attacks in Nigeria’s restive north followed a threat last week by the radical Boko Haram sect that it would escalate attacks in the region.

   The sect is responsible for a string of killings which have targeted security officers, community leaders and clerics in Nigeria’s northeast. Most of their attacks have occurred in the city of Maiduguri. Last week, the group expanded its reach with a suicide bombing on police headquarters in the capital of Abuja.

   But police said Tuesday they believe the sect is only responsible for one of Monday’s killings.

   Police in Maiduguri said motorcycle-mounted gunmen from the group shot dead an officer of the Nigerian Civil Defense Corps on Monday. The corps helps the police to prevent crime and its officers are unarmed.

   Police spokesman Lawal Abdullahi said the gunmen followed the officer after he closed from work and shot him dead at his house - a typical example of the drive-by killings that have become Boko Haram’s signature.

   Police said they doubt that Boko Haram was responsible for a separate attack that left six people dead in the town of Kankara, more than 440 miles (700 kilometers) from Maiduguri. The attack, far out of Boko Haram’s normal area, was the first such attack in its state, police said.

   National police spokesman Olusola Amore said gunmen who killed five police officers and a bystander in a bank robbery and another attack on a nearby police station were robbers and opportunists who  emulated Boko Haram to throw police off their trail.

   Witnesses said the assailants shouted “God is great” in Arabic, leading them to fear they were Boko Haram members. They also threw money to bystanders, witnesses said, creating the impression that their motive was not financial.

   “Boko Haram isn’t after money,” he said, “but we know that people will capitalize on Boko Haram.”    Boko Haram, whose name means “Western education is sacrilege” in  the local Hausa language, wants the implementation of strict Shariah law across Nigeria’s north.

   Amore said police have seen copycat criminals emerge before. In Nigeria’s oil-rich delta, kidnappers first pretended to belong to southern militant groups, he said, but now kidnappings are purely a  moneymaking business.

   “Boko Haram or not, the police will find the culprits,” he said.