A post card received by the Coimbatore police commissioner has threatened to blow up Tamil Nadu Chief Minister M Karunanidhi using a human bomb on September 15.

The card, purportedly written by 'Al-Umma-Madhani Iyakkam, in Tamil has said that Karunanidhi, after returning to power, had promised to relax the age ceiling for recruitment to police from 24 to 29. However, it was relaxed only for SC/ST candidates, which was "totally condemnable".

The chief minister should officially declare the relaxation in age during the inauguration of Kalaignar TV on September 15, the card demanded. It sought reservation for Muslim candidates in police department and reduction of required height from 168 cm to 163 cm. "If not, 'Kalaignar'(Karunanidhi) would be eliminated through human bomb," the card, bearing the seal of Peelamedu post office in the city, threatened. Police Commissioner C K Gandhirajan said that investigations were on to nab the sender.