The two main suspects in the Islamist attack on the Charlie Hebdo magazine in Paris are said to have robbed a service station in the north of France.
Twelve people, including two police guards, were killed in the attack.
French media reports that Cherif and Said Kouachi stole food and petrol, firing shots as they struck at the roadside stop near Villers-Cotterets in the Aisne region.
Earlier, a gunman shot dead a policewoman south of Paris and fled.
It is unclear if the attack in Montrouge, in which a second person was seriously injured, was linked to the Charlie Hebdo shooting, but French prosecutors say they are treating it as a "terrorist act", AFP reported.
According to the manager of the service station, the attackers fit the description of the two men, and were heavily armed with Kalashnikovs and rocket-propelled grenade launchers.
They are said to have driven off in a Renault Clio, apparently the same vehicle hijacked in Paris soon after the attack.
Earlier, the Police made seven arrests as they hunt for two named suspects.
The seven, were detained in the towns of Reims and Charleville-Mezieres, as well as in the Paris area, police said.
Photos have been released of two brothers suspected of involvement in the attack, which killed eight journalists, two police officers, a maintenance worker and a visitor to the newsroom.
Protests and vigils over the attack, the deadliest the country has seen in decades, have been held across France and in other countries around the world, the BBC reported.
Tributes were held in Wellington and Christchurch on Thursday night, and there will be one in Auckland on Friday evening.
French President Francois Hollande called it a "cowardly murder" and declared a day of national mourning.
He said the country's tradition of free speech had been attacked and called on all French people to stand together. "Our best weapon is our unity," Mr Hollande said in a televised address.
Security has been stepped up across France in the wake of the attack, with Paris placed on the highest alert.
Media reports described Cherif Kouachi as a militant sentenced in 2008 to three years in prison for belonging to a group sending jihadist fighters to Iraq.
Anti-terrorism police searching for the suspects and links to them are reported to have carried out searches in Reims, Strasbourg and Paris. A Reuters reporter in Reims saw police secure a building before a forensics team entered an apartment while dozens of residents looked on.
Witnesses tell of deadly attack
Satirical weekly Charlie Hebdo has courted controversy in the past with its irreverent take on news and current affairs. It was firebombed in November 2011 a day after it carried a caricature of the Prophet Muhammad.
The attack took place as the magazine was holding its weekly editorial meeting. French media have named three cartoonists killed in the attack as Cabu, Tignous and Wolinski, as well as Charlie Hebdo contributor and French economist Bernard Maris.
Another victim, Charlie Hebdo editor Stephane Charbonnier, 47, had received death threats in the past and was living under police protection.
Cartoonist Corinne Rey said the hooded gunmen entered the building after forcing her to enter the code to open the door, the BBC reported.
"They said they belonged to al-Qaeda," she said, adding they had spoken in fluent French.
Eyewitnesses said they heard as many as 50 shots fired by the attackers both inside the Charlie Hebdo office and on the streets outside.
The gunmen were captured on amateur video shooting one injured police officer at point blank range in the head on the pavement outside.
They were heard shouting "we have avenged the Prophet Muhammad" and "God is Great" in Arabic ("Allahu Akbar").
Police said the masked gunmen fled to northern Paris, before abandoning their car and hijacking a second one.
Paris prosecutor Francois Molins said 11 people had been wounded in the attack, four of them seriously.
'Je suis Charlie'
The killings have been condemned by leaders worldwide, with US President Barack Obama offering to help France track down those responsible.
Al-Azhar University in Cairo - Sunni Islam's leading centre of learning - called the attack "criminal" and said "Islam denounces any violence".
The Arab League also condemned the attack. Pope Francis called it "abominable".
Angela Merkel and I met today. We're united in our condemnation of the horrifying Paris murders. pic.twitter.com/oSM2us6I8I— David Cameron (@David_Cameron) January 7, 2015
Thousands of people have gathered at the Place de la Republique in central Paris for a vigil, many holding up placards saying "Je suis Charlie" ("I am Charlie"), referring to a hashtag that is trending on Twitter in solidarity with the victims.
Charlie Hebdo's website, which went offline during the attack, is displaying the single image of "Je suis Charlie" on a black banner. Other major newspapers are displaying similar banners.
It is the deadliest attack in France since 1961, when a bomb planted by far-right militants opposed to plans for Algerian independence killed 28 people on a train.
- BBC / Reuters / AFP