Pakistan was on high alert on Monday and the army asked to stand by in Lahore, declared "the most sensitive city", in view of Muharram and the suicide bombing in Peshawar two days earlier.
Punjab Chief Minister Chaudhry Pervaiz Elahi said the province's 23 districts had been declared sensitive, the Daily Times reported on Monday.
Crisis management centres have been set up across the province and the army could be called in the event of an emergency, he said.
The media on Monday reported the arrests of a large number of radicals suspected to be linked to sectarian violence.
Elahi clarified that the suicide attack in Peshawar Saturday, in which 14 people were killed, was not part of sectarian violence.
Shia and Sunni scholars were cooperating to maintain peace and tranquility during Muharram.
He said "anti-state elements" were trying to instigate sectarian hatred.