A supporter of Gichugu MP Njogu Barua was hit with a stone as rival groups clashed at General Kassam Njogu Stadium during Jamhuri Day celebrations Monday.
Elias Comba was hit on the forehead by a 'flying' stone thrown by a rival group that had arrived at the stadium chanting slogans.
He was also stabbed in the shoulder with a knife.
The victim was rushed to the nearby Kianyaga Hospital for first aid before the MP drove him to Nairobi for treatment.
It all began when an aspirant for the Gichugu seat arrived at the venue riding a boda boda amid cheers from his supporters who accompanied him.
Mr Barua's supporters who were close to the dias blocked the entourage from disrupting the event, which resulted in a stampede.
It was during the chaos that Mr Comba was injured.
Police managed to repulse the 'intruders' but the aspirant remained on the dais under tight security to escape the wrath of the MP's enraged supporters.
Following the incident, Barua said he now fears for his life and urged the national government to stamp out such behaviour.
The celebrations went on to the end amid tension although no one has been arrested so far.