Traces of DNA on an orange juice bottle and a surveillance of a man praying in a mall led to the arrest on Wednesday of a 22-year-old suspect accused of stabbing a French soldier who was patrolling a crowded area outside Paris, the Associated Press reported. 

Alexandre was captured on camera on Saturday offering a Muslim prayer in a corner of a buy shopping mall 10 minutes before he went after the soldier with a knife in the La Defense financial and shopping district, prosecutor Francois Molins said,

"The suspect implicitly confessed when he told police, 'I know why you're here," Molins said Wednesday. "Given the attack in London, immediately Saturday we considered the possibility this was terrorism."

French security forces have been on heightened alert since the military intervened in the African nation of Mali in January to regain territory seized by Islamic radicals. Yet even before the French military action in Mali, French soldiers were considered possible targets at home by local radicals.

Last year, three French paratroopers were killed by a man police described as a French-born Islamic extremist. Mohamed Merah went on to attack a Jewish school in southern France, killing a rabbi and three Jewish children in March 2012 before being killed later that month in a gun battle with police.

"I have said before there are dozens, if not hundreds of potential Merahs in our country," Interior Minister Manuel Valls said.