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.