Unidentified persons assaulted a Congress worker, triggering a tense stand-off between activists of the Communist Party of India (Marxist) (CPI(M) and the United Democratic Front (UDF) in the city on Friday.

The police prevented the UDF activists from marching to the CPI(M)'s State headquarters at AKG Centre in protest against the attack on their party colleague. They spoke to the UDF and the CPI(M) leaders to prevent any further escalation of violence.

The chain of events that caused the stand-off occurred on Thursday. A group of CPI(M) activists prevented Congress activists from putting Congress flags on the electric posts in front of AKG Centre to hail the victory of their candidate K. Muraleedharan from the Vattiyurkavu Assembly constituency.

On Friday morning, a group of persons, suspected to be CPI(M) activists, attacked Antony Thomas, a Congress worker who headed the team which put up his party's flags and festoons in front of AKG Centre, when he arrived for work at the fish market at Pangode.

Mr. Thomas was admitted to General Hospital. Congress leaders, including Mr. Muraleedharan, visited him. The police later booked three CPI(M) activists on the charge of simple assault in connection with the attack on Mr. Thomas. The police have posted a picket in front of AKG Centre, the Kerala Pradesh Congress Committee office, and the district headquarters of either party to prevent further violence.