French investigators are trying to establish whether the three Islamist extremists who carried out the deadly terror attacks in Paris were part of a larger terrorist cell. They are also trying to determine whether these extremists had links to the world’s biggest terrorist groups. CCTV’s Kate Parkinson reported the story from Paris.

Paris’ three days of terror started with an attack on the office of French satirical weekly Charlie Hebdo. Amateur video showed two masked gunmen, later identified as Cherif and Said Kouachi, shortly after they unleashed a hail of bullets during the morning editorial meeting.

Paris was put on maximum alert and a major manhunt was launched. Twelve people were left dead and two gunmen were on the run.

The next morning, there was another shooting, leaving one policewoman killed in the southern Paris suburb of Montrouge. Authorities later confirmed the gunman, Amedy Coulibaly, was linked to the Kouachi brothers.

By Friday morning police were closing in on the two Charlie Hebdo suspects. There was a shootout with police, a high speed car chase and then the fugitives sought refuge in a print works. Elite forces moved in and the suspects were surrounded.

As the tense standoff continued in Dammartin-en-Goele, fresh terror descended on eastern Paris. Amedy Coulibaly stormed a Jewish supermarket, killing four shoppers and taking others hostage. He threatened to kill them all unless the Kouachi brothers were allowed to go free. Both sieges came to an end almost simultaneously.

Just before 5pm local time, there were explosions and gunfire in Dammartin-en-Goele. The two brothers, who had told local media they would die “martyrs'” deaths,  emerged from the building, firing at police. Both were killed.

Moments later explosions were heard at the Paris supermarket as elite forces stormed the building, killing Coulibaly and freeing the hostages. France’s three days of terror was over, and the terrorists had killed 17 people.

As investigators tracked links between the attacks, they uncovered a complex network of accomplices. In 2008, Cherif Kouachi was sentenced to three years in jail on terrorism conspiracy charges. This is where he met al-Qaeda recruiter Djamel Beghal.

Coulibaly spent most of the past decade in and out of prison and it’s believed that’s where he became radicalized. Coulibaly’s wife quickly became France’s most wanted woman. Investigators said last year approximately 500 calls were made between Hayat Boumeddience and the wife of Cherif Kouachi. Authorities believe she is now in Syria.

Coulibaly claimed he acted on behalf of the Islamic State militant group. The group has lauded the attack, but has not claimed responsibility.

In 2011, both of the Kouachi brothers are believed to have traveled to Yemen for weapons training.

Days after the attacks, al-Qaeda in Yemen released a video claiming responsibility for Paris attack.

The events are still under investigation and and a full picture is not likely to emerge for months or even years.