Two suspects in the Paris magazine massacre have been located in northern France, according to reports.

Local media said two suspects in the Charlie Hebdo attack were seen armed and getting into a Renault Clio in Aisne, a region to the north-east of the capital.

The sighting was said to have been reported to police by a petrol station worker.

It comes after police and security forces mounted a nationwide manhunt for brothers Said Kouachi and Cherif Kouachi.

The operation was launched after masked gunmen stormed the Paris offices of Charlie Hebdo, killing 12 people in France's worst terrorist atrocity since 1961.

Meanwhile, police are also searching for the perpetrator of a separate shooting in which a policewoman was killed just outside Paris this morning.

It is unclear whether there is any link between the two incidents.

Today's attack took place early this morning when the officer stopped to investigate a traffic accident. The second casualty was a street sweeper.

"There was an officer in front of a white car and a man running away who shot," said witness Ahmed Sassi. He said the gunman was dressed in dark clothes.

The perpetrator fled and is still at large, France's top security official Bernard Cazenueve said. He travelled to the scene after leaving an emergency government meeting.

France is on its highest level of terror alert after suffering its worst attack since 1961 when masked gunmen armed with Kalashnikovs burst into the Paris offices of Charlie Hebdo yesterday morning and opened fire, killing eight journalists, two police officers, a maintenance worker and a visitor.

The magazine had been threatened before for its caricatures of the prophet Muhammed. The attackers shouted "We have avenged the prophet" after the shooting. No group has yet claimed responsibility for the atrocity.

Police searching for those behind yesterday's atrocity have made seven arrests but the operation to find two prime suspects continues.

Images of the Kouachi brothers were released by police last night, as a third man handed himself in.

Hamyd Mourad, 18, surrendered to police, after hearing his name on the news in connection with the attack, a judicial official said.

Cherif Kouachi was convicted of terrorism charges in 2008 for helping funnel fighters to Iraq's insurgency and sentenced to 18 months in prison, according to reports.