The BBC's Owen Bennett-Jones: "Nawaz Sharif will be pleased with the support"

Denouncing members of the Senate, Pakistan's upper house, speakers at the rally described the country as a Muslim state that could only have an Islamic system of justice.

The rally, the first of its kind, was blocked from getting too near to the parliament buildings and ended without serious incident.

Speakers from organisations comprising Sunni Moslems called for the Senate to be abolished if it refused to pass the law.

Gun-ho: Noisy but peaceful demonstration

The lower house of parliament has already passed Mr Sharif's proposals but he continues to face vehement opposition from other parties.

He requires a two-thirds majority in the Senate to push through the constitutional change but does not hold a majority.

Mr Sharif's opponents accuse the prime minister of attempting to seize more power for himself in the guise of Sharia law.

If Pakistan introduced a Sharia system, the government would be obliged to promote what it saw as good for society under the terms of Islamic justice.

Sharif: Critics say he wants more power

Earlier in the week during a provincial tour to gain support, Mr Sharif said that Sharia would ensure swift justice for ordinary people.

He told supporters that he favours a system similar to that introduced by the Taleban in Afghanistan.

The proposals include the public hanging of murderers and rapists after having their cases dealt with in less than a week.

But opposition groups and human rights campaigners predict that the legislation, if passed, would lead to increasing sectarian and religious tension.