A Nigerian security official says the Islamic extremist rebels of Boko Haram are trying to spread their violent campaign across Nigeria including Lagos, the country's largest city.

Tony Opuiyo, spokesman of the Department of State Services, Nigeria's intelligence agency, said Sunday there has been a sudden influx of Boko Haram members in Lagos and other parts of the country, after security forces pushed the militants from northeastern centers.

Opuiyo announced that security agencies had arrested 14 Boko Haram suspects outside the northeast in the last two months, including cell leaders, some of whom admitted to involvement in recent suicide attacks. Authorities on Friday said they arrested a teenager who was spying on the capital's main airport for Boko Haram. The six-year-old Islamic uprising has killed an estimated 20,000 people.