Nigerian soldiers have blocked roads out of a key northeastern city to deprive Boko Haram fighters of supplies in remote towns they control, the army has said.
The military said on Sunday that its offensive against the group, which followed a declaration of a state of emergency in three northeastern states, was aimed at re-establishing Nigeria's "territorial integrity".
The assault on Boko Haram, which has said it wants to create an Islamic state, included air strikes on strongholds in remote parts of northeastern Borno state, and has spread to the state capital Maiduguri, the fighters' traditional home base.
Residents said on Sunday the base had been blockaded.
"There is a huge build-up of trucks loaded with essential commodities... along the Baga road on the way out of Maiduguri to the northern part of the state," said Ibrahim Yahaya.
"The drivers said they have been prevented by the military from going northward," he told the AFP news agency by email.
'Run out of supplies'
The phone network in Borno has all but collapsed since president Goodluck Jonathan on Tuesday declared a state of emergency there and in two neighbouring states, Adamawa and Yobe.
Chris Olukolade, a defence spokesman, said in a statement on Saturday that fighters on the run were scrambling for key supplies like fuel. He urged residents to report anyone trying to buy large quantities of fuel.
The supply shortage has begun to bite in the town of Gomboru Ngala, on the border with Cameroon, where some Borno residents have fled to escape the air raids.
"Trucks bringing in goods from Maiduguri have ceased since last week," said resident Grema Babagoni. He said the supply shortage has pushed prices up by as much as 25 percent.
"If the blockade continues for some time we may completely run out of supplies," he told AFP.
On Saturday, the army declared a 24-hour curfew in a dozen neighbourhoods of Maiduguri, Boko Haram's stronghold.
The curfew in the main city in Borno state came as soldiers continued the government's emergency campaign against fighters in the region on Saturday.
A defence spokesman also said the military had seized stockpiles of weapons including rocket-propelled grenades, guns and ammunition from areas around Maiduguri.
Boko Haram has carried out scores of attacks in recent years, and has become emboldened and better armed in recent months.