The incident occurred as Singh was on his way to attend the 85th birthday celebrations of former Meghalaya Governor M M Jacob at a college here after inaugurating the 90th anniversary celebrations of 'Mathrubhumi'.
Bharathiya Janata Yuva Morcha Ernakulam District President Sreekanth Sreedharan was taken into custody and allegedly beaten up and taken to the central police station.
BJP District President P J Thomas alleged that police used third degree methods to torture the youth activist, who has been admitted to hospital.
Yesterday, five BJYM activists were arrested in Thiruvananthapuram for attempting to jump before Singh's motorcade to wave black flags.