Pakistani paramilitary troops went house to house rounding up dozens of men in a restive neighbourhood on Tuesday as part of a crackdown on soaring violence in Pakistan?s largest city.

The operation in the Orangi Town neighbourhood came after a week of targeted killings that left more than 40 people dead in Karachi, a city of 18 million people and a long history of ethnic, religious and other violence, much of it believed linked to major political parties.

But it was unclear how serious the crackdown by the Army Rangers really was, or whether it would have any long-term impact.

Pakistani security forces often carry out such operations in various parts of the country as a show of force, including against Taliban and al-Qaeda linked groups in the northwest. The suspects detained are typically freed or held for long periods without being charged. Cases rarely make it to the courts.

Orangi Town, a city on Karachi?s western side, was the focus on Tuesday because it was the worst hit during the recent spate of violence. Some 15 people, including several political activists, fell prey to unknown gunmen in the past week.

Around 1,500 paramilitary troops cordoned off part of the neighbourhood and conducted house to house searches, said Army Rangers? spokesman, Maj. Farooq Bilal. Media were not allowed into the neighbourhood.

?This operation will go on until the objectives are achieved - there is no time limit,? Maj. Bilal said. ?We have detained some people who will go through a screening process.?

Karachi, a port city that is the country?s main financial hub, occasionally endures such spates of violence. Much of it is believed linked to the three main parties in the city, the Pakistan People?s Party, the Awami National Party and the most powerful locally - the Muttahida Qaumi Movement.

Despite officially being allies on the provincial level, the parties compete with one another for supremacy in Karachi, especially the ANP and the MQM. The three parties are also allies in the federal ruling coalition - an alliance that barely survived an MQM threat to switch to the opposition late last year.

The People?s Party, which has the most seats in parliament, needs to keep the MQM and the ANP happy to keep its government intact. That means it has to tread carefully in any crackdown it undertakes in Karachi.

In the northwest, police said Taliban fighters shot dead four suspected robbers that authorities also were chasing. The four bodies were found on Tuesday along a road in Hangu district, said police official Islam-ud-Din.

A note identified the men and said they confessed to their crime. Mr. Din said police had confirmed that the four were suspected robbers on their wanted list.

Taliban militants in northwest Pakistan frequently flog or execute alleged criminals in a bid to gain public sympathy by imposing order in a largely lawless area. Hangu is located near the Orakzai tribal region, where Pakistan?s army is waging an offensive against Islamist militants.

Elsewhere in the country, a roadside bomb exploded near a car killing two civilians in southwest Baluchistan province. The blast occurred in the Turbat district said Sher Jan, a local government official. Baluchistan has long been gripped by a low-level insurgency which aims to gain more autonomy for the province.

More In: International | News