The incident took place in the premises of the Corporation last evening, when Yadav was about to leave the office for his residence, police added.
After the attack, the injured Congress corporator was rushed to the district hospital, from where he was taken to the CHL hospital in Nanakheda. However, he succumbed to his injuries on the way, police said.
According to police, those present at the site tried to catch hold of the assailant, but he managed to escape.