Nigerian police are conducting 24-hour surveillance of all telecom installations after the terrorist group Boko Haram claimed responsibility for a recent spate of attacks on mobile phone towers in the north.

Boko Haram has accused the telecom companies of breaking their "ethical obligations" and helping security agencies spy on its members.

So far, the groups activities have affected nine companies, though it is not yet clear how much damage has been caused. The cost of a communications tower is estimated at around $1 million, the BBC reported.

Nigerian police chief Mohammed Abubakar assured telecom companies that special units would closely monitor all installations.

"With that guarantee, we will continue to provide services so we do not intend to discontinue services," Gbenga Adebayo, chairman of the Association of Licensed Telecom Companies of Nigeria, told the BBC.

Boko Haram is a militant Islamist sect that aims to implement Sharia law across Nigeria. It is claimed responsibility for a series of attacks on government and civilian targets, killing over 900 people since 2009, Human Rights Watch reported.