Addressing the rally on phone, MQM's London-based chief Altaf Hussain said Pakistan's peace and security are under threat and it is important that measures be taken to safeguard stability.
Hussain also said the country's existence is threatened, and those who support the Taliban are hypocrites and not Pakistan's friends.
He said external forces had "abused" Pakistan for their own agendas and the army should step forward as it has backing of every Pakistani. "If we're strong internally, no external power can disintegrate us," Hussain said.
He said he had warned people about the threat posed by Talibanisation years ago but his statement about Karachi being infiltrated by militants was made fun of.
The rally, held at Shahra-e-Quaideen, was attended by tens of thousands of people, including a large number of women and children. It was organised days after the federal government suspended peace talks with the banned Tehrik-e-Taliban Pakistan after a militant faction executed 23 troops.