Authorities are battling to halt gunfights raging across the key port city - used by NATO to ship supplies to Afghanistan - where political, ethnic and criminal rivalries left more than 200 people dead last month.

The provincial government is offering 10 million rupees ($115,000) to citizens who provide information leading to arrests of those responsible for the violence, the worst in the city since 1995.

Local government official Sharfuddin Memon told AFP the extra paramilitary soldiers and policemen entered the city's troubled western neighbourhoods on Tuesday night.

"Some suspects have been detained," after house to house searches, he added.

Wajid Durrani, police chief of the southern Sindh province, of which Karachi is the capital, said police had made 24 arrests and some officials said calm had been restored.

AFP