Paris attacks gendarmes
An armed French gendarme stands along the highway as gendarmes check vehicles near ParisREUTERS/Pascal Rossignol

French authorities are on the hunt for a second fugitive who was directly involved in the terror attacks on Paris on 13 November. The officers are looking for the suspect – who has not been named – in addition to Salah Abdeslam, who has been dubbed "Public Enemy Number One".

According to an Associated Press (AP) report, three officials speaking on condition of anonymity said that an analysis of the attacks "indicated that one person directly involved was unaccounted for". The series of assaults claimed the lives of 129 people and wounded more than 350.

Speaking to Reuters, a justice official said: "We are in the process of determining how many there may have been. Nothing is ruled out. There's a very strong theory that there was one more, but there may have been even more."

The brother of 26-year-old Belgian-born Salah Abdeslam has urged his sibling to hand himself in to authorities. Mohamed Abdeslam told French channel BFMTV: "Of course I call on him to turn himself over to the police. The best would be for him to give himself up so that justice can shed all the light on this." Following the attack, Mohamed was arrested and questioned, but was later released.

The news of a second fugitive came as France launched further air strikes on Islamic State (Isis) positions in Syria. US Secretary of State John Kerry also hinted at a potential ceasefire in Syria in order to eliminate IS.

Seven of the assailants died on 13 November. Six of them detonated their suicide vests while a seventh was killed by police gunfire. France's interior minister, Bernard Cazeneuve, has admitted that "the majority of those who were involved in this attack were unknown to our services".