At least 24 mobile phone masts have been attacked across northern Nigeria, industry officials say.
A military spokesman blamed the militant Islamist group Boko Haram for the first such attacks on nine mobile phone companies.
Boko Haram has previously accused the firms of working with security agencies to track down its members.
Experts say the damage could run into millions of dollars.
Gunshots and explosions were heard and fires raged as mobile phone pasts were targeted in northern Nigeria's main city, Kano, as well as the cities of Maiduguri, Gombe and Bauchi.
An attack also happened in the town of Potiskum.
Military joint task force spokesman for Maiduguri Lt Col Sagir Musa told the BBC the security forces suspected that Boko Haram had carried out the attacks.
It was a new trend in the violence carried out by the group, he said.
'Collusion'
Nine companies had reported infrastructural damage to 24 masts since Wednesday, said Gbenga Adebayo, the chairman of the Association of Licensed Telecommunications Operators of Nigeria, AP news agency reports.
Companies targeted include South African telecom giant MTN as well the United Arab Emirates firm Etisalat, AFP news agency reports.
"We confirm that like all the other major telcos, some of MTN's installations in northern Nigeria have been damaged by unknown persons," spokeswoman Funmilayo Omogbenigun is quoted as saying.
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