Dusseldorf (dpa) - One day before the German city of Cologne was due to elect a new mayor, independent candidate Henriette Reker was stabbed Saturday morning on the campaign trail at a weekly market.A man armed with a knife attacked Reker shortly after 9 am (0700 GMT) at a campaign stall run by the centre-right Christian Democratic Union (CDU), injuring her, a police spokesman said.Two people were seriously wounded and three slightly wounded in the ensuing scuffle.It was not immediately clear how seriously hurt the 58-year-old mayoral candidate was. Emergency services deployed a helicopter after the attack.The attacker, aged in his 30s, was arrested at the scene, where police and the public prosecutor launched an investigation.The weekly market is held in the city district of Braunsfeld. Reker‘s colleague Frederik Schorn told dpa that at least one of her campaign team had also been injured in the attack.The people of Cologne elect a new mayor on Sunday. Reker is being supported by the CDU, the Greens and the liberal Free Democratic Party (FDP).