Pakistani opposition leader Nawaz Sharif on Sunday ignored his house arrest and left home to lead a protest march to the capital as police clashed with his supporters to break their advance.

Sharif, leader of the Pakistan Muslim League, drove to a supporters' rally in Lahore and from there set off a convoy of cars heading to Islamabad. The caravan will stop in Rawalpindi on Monday so Sharif can fetch his brother, Shahbaz, who is also under house arrest.

Meanwhile, authorities have blocked roads leading to Islamabad, arrested activists and banned rallies in the city.

The Sharif brothers and their supporters are demanding from President Asif Ali Zardari the reinstatement of judges sacked by the previous government. They are also protesting their disqualification from politics.

Zardari has promised to reinstate the judges upon assuming power last year but has yet to do so.