Thousands of people fled their homes in northwestern Nigeria this week after the leader of one of the armed gangs in the region ordered them out in retaliation for a security raid, officials and residents said on Wednesday.

Officials say Bello Turji leads one of many armed gangs which terrorise predominantly Muslim northwest Nigeria, killing and abducting residents, farmers, students and motorists for ransom.

Violence in Africa's most populous country has attracted the attention of U.S. President Donald Trump, who has accused the government of failing to prevent the killing of Christians. Nigeria says gangs and militants target both Christians and Muslims and that Christians are not systematically persecuted.

Residents of the northwestern Tidibale community say Turji suspects a tip-off from the community to security forces led to recent military operations that killed one of his men.

Turji visited Tidibale three days ago and killed three people to enforce his order to the community to leave, said Basharu Altine Guyawa, Sokoto state coordinator of the Movement for Social Justice and Good Governance.

"He told them if anyone remains when he returns, they will be killed. He said he will not spare even a chicken," Guyawa said.

Islamist militants from Islamic State West Africa Province (ISWAP) and Boko Haram are also active in the region, where insurgency has persisted for 15 years. Last month, the United States carried out a strike against Islamic State militants in the northwest.

The Sokoto police spokesperson said residents were fleeing Tidibale community for fear of attack and that more police had been deployed to the area.

Local authorities have been evacuating people by truck to Isa, about 50 km (30 miles) away. Muhammad Ibrahim, secretary of the community security committee in Isa, said more than 3,000 people have been moved, including into the town's schools.

"There is a humanitarian crisis. Educational activities have stopped," Ibrahim said.

Tidibale lies about 100 km east of the state capital Sokoto. Local activists warn that dozens of villages have been abandoned as violence by armed gangs escalates in Nigeria's northwest.

"The past three weeks were horrific. Killings and abductions have persisted," said Usman Musa, a father of 15 who fled to Isa. "The government has ignored us. I want them to flush these bandits out."