The independent candidate in the mayoral elections was slashed in the neck at a political meeting in the German city of Cologne. An aide who was with her and three other people who tried to overpower the assailant were also wounded on Saturday (17 October).
Reker's injuries are said to be serious, but she is expected to survive following emergency surgery. The attack was reportedly motivated by her policies over refugees. A 44-year-old man has been arrested according to police.
The mayoral candidate was at an information stand for Chancellor Angela Merkel's Christian Democrats (CDU) party when she apparently offered a man one of her rosettes. He responded by stabbing her, according to BILD.
Councillor Dr Jürgen Beam, who witness the attack said: "The perpetrator had two knives. He went up to her and stabbed her. Then he attacked other people who wanted to come to her aid. The attacker said he would save society from such people."
Other eyewitnesses said the man made no efforts to escape but stayed until police arrived, who then arrested him according to a Deutsche Welle report. Initial investigations suggest it was a "politically motivated" attack, say police.
The mayoral election was due to take place on Sunday but her main rival, Social Democrat Jochen Ott, suspended his campaign because of the attack. The outgoing mayor Juergen Roters said he was "deeply shocked" by the incident.
As social Deputy Mayor of the city of Cologne, Henriette Reker has spoken out in favour of tolerance towards refugees. She is also involved in campaigns speaking out on discrimination, exclusion of foreign citizens and against racism.