Paramilitary forces raided the headquarters of a powerful Karachi political party and arrested two members on Friday, officials said, in a sign of deepening tensions between the army and politicians controlling the biggest and richest city.
Many fear the showdown may threaten the stability of the financial hub that generates half of government revenue and is home to 20 million people, or upset the delicate balance between the fledgling civilian government and the powerful military, which has a history of coups.
The paramilitary Sindh Rangers, which fall under military command, said they raided the Muttahida Qaumi Movement (MQM) because the party had been making hate speech.
The MQM, Pakistan's fourth largest party, traditionally represents the descendents of Urdu-speakers who migrated from India after the creation of Pakistan in 1947. It was involved in bloody factional battles in Karachi in the 1990s and now holds the majority of the city's legislative seats.
"Those apprehended tonight ... have been arranging and facilitating hate speeches against peace of Karachi," Director General Sindh Rangers, Major General Bilal Akbar tweeted.
MQM's leader Altaf Hussain, who lives in exile in London, has repeatedly accused the military of targeting his party in long, rambling speeches. Hundreds of party workers have been arrested in a crackdown aimed at criminals and militants.
"Workers should be mentally prepared for more such raids; we will see how many workers are arrested," Hussain said in a broadcasted telephone address after the raid.
British authorities are currently investigating Hussain for money laundering. They are also seeking to question MQM members over the murder of a dissident MQM activist in London.
Two MQM members - a former provincial legislator and the chair of the decision-making central committee in Karachi - were detained in Friday's raid for "hate speech".
"More arrests will be made in the near future," Rangers spokesman Major Sibtain Rizvi said in a statement.
Party spokesman Farooq Sattar condemned the raid to party members who gathered to protest afterward.
"MQM is the only political party whose head office is being raided by Rangers," he told the crowd.
Friday's arrests follow a raid on the same address on March 11, when authorities said dozens of weapons were recovered and a suspect wanted for the murder of a journalist detained. The MQM said the weapons were planted and the suspect smuggled in.
Police officials privately accuse the MQM of operating like a mafia to maintain its tight control on power. But the party has always strongly denied being involved in violence.