NEW DELHI. Friday, March 26 -- The Pakistani Government reasserted control over East Pakistan this morning and banned all political activity, the Pakistan Radio announced in a broadcast monitored here.

The broadcast said that the army has taken control of the nation's eastern half. Martial law was declared there three and a half weeks ago, but the central Government and the army had refrained from cracking down on a widespread campaign of civil disobedience led by Sheik Mujibur Rahman, the province's political leader, and his Awami League.

Prior to the broadcast announcement, President Agha Mohammed Yahya Khan broke off negotiations in Dacca with
the Sheik and returned today to Karachi with his staff.

Reports from Dacca, the capital of East Pakistan, said that the army was called out last night and that the Intercontinental Hotel had been surrounded by troops. All foreigners were told not to leave the hotel.

However, a dispatch from Karachi said that advisors of President Yahya Khan remained in Dacca to continue talks with Sheik Mujib on his demand for autonomy for the Eastern area.

Troops in the East Pakistani port of Chittagong reportedly fired yesterday o mobs ripping up railroad tracks leading to an army compound and surrounding a ship believed to contain military supplies. Sheik Mujib called a general strike for Saturday and demanded that President Yahya Khan "order immediate cessation of such military operations."