A senior France official said that some 130 French nationals or immigrants are fighting in Syria, expressing concerns about consequences of these extremists returning to the country when the fight is over. Manuel Valls, the French Interior minister, said on Thursday that the number is worrying for French national security. According to Valls, hundreds of home-grown militants were signing up to fight in Syria, and warned they could pose a security threat when they return to France. More than 300 French nationals or residents are either currently fighting in Syria, are known to have plans to go and fight, or have recently returned from Syria, the minister told France Inter radio. Most of them were young men with a delinquent past who had become radicalized, he said. \"This is a phenomenon which worries me because they represent a potential danger when they return to our soil,\" Valls said. \"We have to be extremely attentive.\" According to British defense consultancy IHS Jane\'s, up to 10,000 militants from all over the world are fighting alongside foreign-backed rebels in Syria, while other independent sources put the number at 50,000. At least one French national has been killed fighting in Syria. A 22-year-old French national from Toulouse was killed in a clash with government troops in August. Syria has been experiencing unrest since March 2011 with organized attacks by well-armed gangs against Syrian police forces and border guards being reported across the country. Hundreds of people, including members of the security forces, have been killed, when some protest rallies turned into armed clashes. The government blames outlaws, saboteurs, and armed groups for the deaths, stressing that the unrest is being orchestrated from abroad. Tel Aviv, Washington and some Arab capitals have been staging various plots to topple President Bashar al-Assad, who is well known in the world for his anti-Israeli stances.