Authorities blame a radical Islamist sect for twin suicide car bombings targeting two major mobile phone companies, an official said Saturday, blacking out a top operator’s network in most of Nigeria’s northern commercial hub.

A suicide bomber drove an explosive-laden car into the facilities of the Nigerian subsidiary of Bharti Airtel of India at about 8am in the city of Kano, said Capt. Iweha Ikedichi, who speaks for a special taskforce deployed in Kano to reduce the threat of the Islamic rebels known as Boko Haram.

The attack left an Airtel worker injured, authorities said. It also damaged a switch station, said James Eze, an Airtel spokesman. He said the company was still assessing how bad the damage was, but declined to comment further.

Switch stations control the network and if they are seriously damaged, the entire network could go down. An Airtel staffer said the targeted switch station covered six northern states, including Kano.

But while Airtel’s network appeared to be down across Kano Sunday, calls to lines in some of the other states went through.

Around the same time as the Airtel attack, another bomber targeted the facilities of the Nigerian subsidiary of South Africa-based MTN Group, about two miles away. That attack was botched by security officers who shot the bomber, causing an explosion at the company’s gate.

The target of the foiled attack was MTN’s switch station, said Funmilayo Omogbenigun, spokeswoman for Nigeria’s largest phone network provider.

Authorities suspect the Boko Haram sect is behind the strike.