Karachi: Almost 24 people have been killed in the ongoing police operation in the densely populated, impoverished and troubled neighbourhood of Lyari that entered its fourth day here Monday in Pakistan.

Law enforcement agencies claimed they have arrested 20 criminals involved in the gangwar  some with bounties on their head.

Meanwhile, protesters stoned vehicles and burnt tyres on a bridge close to the Lyari area to protest against the police operation.

Till Sunday, 22 people were killed in police operation.

In a separate incident on Monday, motorcycle-borne gunmen fired at two passenger buses in Shershah, close to Lyari injuring several passengers three of whom later died in hospital.

Inspector General of Police of Sindh province, Mushtaq Shah told reporters that the police assisted by the Frontier Constabulary had gained notable success by capturing 20 wanted criminals.

"Police has taken control of some areas where these criminals were holed up -- firing rocket propelled grenades and using heavy ammunition against our men," he said.

The official added that some of the arrested carried rewards on their heads.

Families from the area continued to move to safer locations as tension prevailed with markets and shops remaining completely closed.

Gangsters fired rocket propelled grenades in some areas of Lyari injuring eight people this morning.

The operation that began on Friday has seen the police aided by the Frontier Constabulary forces slowly move into the congested and narrow lanes of Lyari which is considered the stronghold of the ruling Pakistan People's Party and Bhutto family.

The area had however been taken over by different criminal gangs in the last few years who are said to have affiliations and are patronised by politicians.