Government minister Marriyum Aurangzeb said the move had nothing to do with elections and police were only complying with court orders.
She claimed that Mr Khan was using his party workers, women and children as human shields to evade arrest and stoke unrest.
Since being ousted from office, Mr Khan has been a vocal critic of the government and the country's army. He has toured the country delivering fiery speeches calling for elections due later this year to be held early.
He has kept up pressure on his successor Shehbaz Sharif with demonstrations and blames him for an assassination attempt in November in which he was wounded in the leg.