Opposition parties said police had raided the homes of their workers and detained hundreds ahead of the planned rally for Chief Justice Iftikhar Mohammad Chaudhry.

Chaudhry, who is fighting a legal battle against his dismissal, is travelling by road from Islamabad to the eastern city of Lahore, where lawyers have promised him a "historic welcome."

Officials said police had blocked roads to prevent Chaudhry's supporters from joining his caravan.

"Thousands of people have joined the caravan of the chief justice despite the police preventing a large number of people from joining us," said Muhammad Ramzan of the Pakistan Bar Council.

Organisers said the planned rally would be the biggest since Musharraf sacked Chaudhry on March 9, sparking a political crisis.

"We expect around 50,000 people to attend the function we are hosting in the honour of chief justice," President Lahore High Court Bar Association Muhammad Ahsan Bhoon told AFP.