KARACHI: Pakistan’s largest city was on edge Wednesday after troops raided the headquarters of a well-known political party, arresting about 20 suspects and seizing weapons, a spokesman said.

The early morning raid in Karachi, the country’s economic hub, took many in this teeming metropolis by surprise, especially since it targeted a prominent party with a presence in the national Parliament.

The troops seized a large cache of assault rifles and detained suspects — including six “known criminals” — from the Muttahida Qaumi Movement’s offices in the heart of the city, said Col. Tahir Mahmood, a spokesman for a Pakistani paramilitary force known as the Rangers.

The spokesman showed the media heavy weapons he said were seized from the offices and for which he said the party did not have licenses. Mahmood claimed MQM sheltered criminals and obstructed life in the neighborhood by placing barricades in the streets.

“Five to six men are those who are criminals and we have their record,” Col. Mahmood told media. “There were certain people who have been awarded death sentences by court.”

MQM’s opponents say the party engages in extortion and frequently kills opposition activists. The MQM denies the allegations, saying its own party workers are targeted by others.

Mahmood said the raid was not politically motivated, but prompted by news that several wanted men were at the headquarters, including one sentenced to death in absentia for the 2011 murder of a young television reporter.

Soldiers sealed the building and handed responsibility for it over to police, he said. It will remain in police custody until an investigation is completed, he said.

But MQM officials hotly disputed Mahmood’s account of the raid. Party leader Faisal Subzwari accused the Rangers of killing one MQM worker and said the weapons were licensed and necessary to guard the offices against Taleban threats. Another party leader, Farooq Sattar, condemned the raid as politically motivated.

The Rangers spokesman made no mention of any firing. A police officer, Saleem Akhtar, said they were investigating the death of one MQM worker.

The MQM controls most of Karachi but is often accused by opponents of using violence to bolster its power. Its leader, Altaf Hussain, has lived in self-imposed exile in Britain since 1992. The party has complained in recent months that their operatives have been targeted in military and police operations designed to quell violence in the city.

Hours later, local media reported that businesses in Karachi and other cities where the party has a presence had started to close.

MQM condemned the raid and insisted that the weapons were all legally held.

“It was all licensed weapons issued to the MPs of the party,” senior MQM leader Haider Abbas Rizvi told AFP. He said it was a disgrace that a leading political party was “being ridiculed in such a ruthless way.”

MQM, whose leader Altaf Hussain lives in exile in London, holds 23 seats in the National Assembly, almost all in Karachi.

The Rangers said there was no resistance during the raid, but television footage showed Rangers soldiers firing gunshots while leaving the offices.

Senior police officer Tahir Noorani told AFP that MQM activist Waqas Ali Shah was shot dead.

The Rangers also rounded up Aamir Khan, a senior MQM leader, who was present at the time of the raid. “We have taken Aamir Khan into custody to inquire about the presence of the criminals with him,” the colonel said.

The raid enraged MQM workers and the party announced a protest. Petrol stations, schools and colleges were closed and public transport also vanished from the roads.