Calcutta, May 7: Waking up to mounting crimes in the city, police launched a special overnight drive.

Last night’s raids ? in areas covered by all the 47 police stations ? netted more than 300 people with criminal antecedents. Twelve firearms and 27 bombs were recovered from them.

Those picked up include hardened criminals who have arrest warrants against them but have been eluding the police.

Four persons were murdered and four robberies recorded in the past fortnight. But both the police and the detective department have failed to make any headway in any of the cases.

The police said the night-long raids came on instructions from the office of the commissioner of police, Prasun Mukherjee.

?Over 190 criminals were rounded up in central Calcutta alone ? covered by nine police stations ? and of them, 40 are hardened criminals. Some firearms were also found,? said Ajay Kumar, the deputy commissioner of police (central).

However, the crackdown does not seem have sent the signals it was meant to. This morning, barely a couple of hours after the raids ended, two groups of traders hurled bombs at each other following a brawl over space at Koley Market under Muchipara police station.

Trouble started when some mango traders found their seats occupied.

The two groups began squabbling, which soon turned violent. They even hurled bombs at each other. Police arrived later and arrested one person.