The manhunt for the two suspects in the killing of 12 people at a satirical magazine in Paris is concentrating on an area northeast of the capital after the men were spotted at a gas station in the region.
Two police sources told Reuters that the men were spotted at a petrol station in the region, were seen armed and in a Renault Clio car at a petrol station on a secondary road in Villiers-Cotterets some 70 kilometers (43 miles) from the French capital.
Bruno Fortier, the mayor of neighboring Crépy-en-Valois, told Reuters helicopters were circling his town and police and anti-terrorism forces were deploying en masse.
"It's an incessant waltz of police cars and trucks," he told Reuters.
Earlier Thursday, a female police officer, who has yet to be named, was killed and a roadsweeper injured in Montrouge south of Paris after an assailant opened fire before fleeing.
French Interior Minister Bernard Cazeneuve told reporters before the officer's death was confirmed that authorities were doing their utmost to identify and arrest the attacker, and he cautioned against jumping to conclusions, The Associated Press reported.
France began a day of mourning for the journalists and police officers shot dead on Wednesday morning by black-hooded gunmen using Kalashnikov assault rifles. French tricolour flags flew at half mast throughout the country.