KARACHI (AFP) - Pakistani security forces raided the offices of the main political party in Karachi on Wednesday, arresting activists and seizing a "huge quantity" of weapons.
The raid on the Muttahida Qaumi Movement (MQM) headquarters, known as "90", sparked an angry response from the party, with workers shutting down large parts of Pakistan's biggest city.
At least one supporter of the MQM, the fourth largest party in parliament, died as government paramilitary Rangers opened fire on protesting activists.
Rangers personnel raided the offices in central Karachi acting on an intelligence tip-off that convicted criminals were hiding inside.
"We have arrested five to six people who had criminal backgrounds," Colonel Tahir Mahmood, who was leading the team, told reporters outside MQM headquarters.
"There were some criminals to whom the court has handed down the death sentence." A Rangers statement said those held included one man sentenced to death for the murder of a television news journalist in 2011.
The statement said a "huge quantity of weapons and ammo" were seized in the raid.
"The finding of weapons carries a question mark and we will investigate it," Mahmood said.
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.
The MQM was founded in 1984 in response to the marginalisation of Mohajirs - migrants who fled India amid the violence of the sub-continent's partition.
Hussain remains a highly influential figure in Karachi, Pakistan's economic centre and main port, wielding effective control over the city from his London home, addressing supporters using a loudspeaker linked to his telephone.
The MQM presents itself as a voice of political moderation and secularism, though critics accuse it of operating as a violent mafia-like organisation.