Armed rioters are reported to have blocked roads and set light to at least four vehicles in the violence-plagued port.

It is also reported that masked armed men also exchanged heavy gunfire with security forces in the central Liquatabad area, but there were no immediate reports of causalities.

The violence was prompted by the government's efforts to destroy what is says are shanties built without permission on government-owned land in the nearby Gharibabad district.

This neighbourhood considered a stronghold of the Muttehida Qami Movement (MQM), Karachi's largest political party.

The authorities have bulldozed dozens of shanties in the low-income area, saying the structures provide shelter to "terrorists and criminals."

The MQM, which represents Urdu-speaking people who migrated from what is now Indian territory when the subcontinent was divided in 1947, in turn accuses the government is engaging in "state-sponsored terrorism".

800 killed this year

Almost 800 people have been reported killed this year in political and religiously motivated violence in Sindh province, where Karachi lies.

Sindh was placed under direct federal rule 30 October following the dismissal of the elected provincial government.

Amnesty International reports that hundreds of people were rounded up and arrested, many of them without charge, during continuing violence.