The chief justice said the Supreme Court wanted to consider fully various legal objections to the quick trial courts.

The courts were set up in November by the Prime Minister, Nawaz Sharif, in an attempt to combat persistent ethnic violence in Karachi by getting the justice process moving more swiftly.

Mr Sharif argued that some cases in Karachi's civilian courts have been held up for years.

"The decision has been taken to protect lives of the people and is in the larger interest of the city and the country," Mr Sharif said.

Karachi has been wracked by violence

But political parties in Pakistan had lodged legal objections to the courts, claiming that they would lead to miscarriages of justice.

Human rights groups have been very critical of the military courts, which have been instructed to complete cases in just three days, with another three days allowed for a final appeal.

One ethnic group representing Urdu-speaking Indians, the Mutahidi Qaumi Movement, has said it is being unfairly targeted by the military courts, and is challenging their legality in the courts.

Two people have already been hanged following convictions from the military courts.

The fate of one man, who had been sentenced to death by a military court, has already been affected by the decision.

He had been due to go to the gallows in the next few days. His fate will now depend on the outcome of the Supreme Court deliberations.

Karachi has suffered endemic violence in recent years, with rival ethnic and political groups battling each other for control.