KARACHI - For more than two decades, Altaf Hussain has wielded control of this freewheeling, violent city of 20 million half a world away from his drab London suburb home.
His arrest on Tuesday by British police has left Pakistan's biggest city on edge and fuelled questions about the future of his political machine.
The 60-year-old is revered by his fiercely loyal supporters -- mainly ethnic Mohajirs who migrated from India at the time of partition, while critics accuse him of running his party as a violent mafia-like organisation.
Party workers appeared to be in a state of shock Wednesday at a protest rally organised on the main thoroughfare of this city and attended by thousands.
Kashif Ahmed Shaikh, a die-hard party supporter, showed off razor-blade cuts on his upper arms.
"I wasn't able to vent my anger on anyone so I did this for my leader," said the 32-year-old at a protest rally over Hussain's arrest in London on money-laundering charges.
"He has done a lot for us and these wounds are just a humble way to express our love and reverence for him. We can even lay down our lives for him," he added.
The sentiments are indicative of how deep passion for politics runs in Karachi, which grew from a small fishing town in the 19th century to Pakistan's economic hub.
It is home to large numbers of all the country's religious and ethnic groups, whose political parties developed armed wings during the 1980s.
The MQM was founded by Hussain in 1984 in response to the marginalisation of Mohajirs -- migrants who fled India amid the violence of the sub-continent's partition.
They are mainly concentrated in the cities of the southern Sindh province, especially Karachi where they form a majority.
Nida Kirmani, an academic at the Lahore University of Management Sciences, said the Mohajir community felt aggrieved by quota systems and preferential treatment for other groups.
"The rhetoric was that they struggled, they sacrificed to come to Pakistan and that's why they should have rights. They believed their migration justified the creation of Pakistan," she said.
Despite the MQM's early successes in bringing development and assistance to Mohajirs, the turbulent city continued to see violent clashes resulting in a military operation in the city in 1992.
Hussain fled the country saying he feared his life to settle in London, where he began to address thousands of supporters in Pakistan by videoconference or simply by phone.
Despite being repeatedly accused of inciting violence during his speeches, British authorities awarded him with a passport in 2002 -- partly due to his party's secular, anti-Taliban outlook.
Hussain wrote to former British prime minister Tony Blair in 2001 offering help against Al-Qaeda in return for the abolition of the country's feared Inter Services Intelligence agency, the British government confirmed two years ago.