Belgium is to go to the International Court of Justice with its legal challenge to Home Secretary Jack Straw's decision on General Augusto Pinochet.

Papers are being lodged at the court in The Hague seeking urgent action to prevent the former dictator from leaving the UK before matters have been resolved in the English courts.

It follows Mr Straw's controversial move to drop extradition proceedings against the general on grounds of ill health.

The home secretary has said he is "minded" to release the general, but has taken submissions to help him with his decision.

Belgium and six human rights groups, including Amnesty International, will also go to the High Court on Wednesday for a hearing to determine whether the matter should go to a full judicial review.

Challenge

Richard Stein, the lawyer acting for the Belgian government, said: "The application filed at the International Court will include an application for provisional measures to ensure Jack Straw takes no steps to allow Pinochet to go while the matter is before the English courts.

"Our substantive case is that he, Mr Straw, should provide proper co-operation to Belgium by allowing the information to be disclosed."

Mr Stein said it was hoped the matter would be heard by the court within days.

He said the grounds Belgium was seeking a judicial review were that Mr Straw should have to provide the authorities there with the medical evidence on which he was basing any decision not to extradite the former dictator to Spain to face torture charges.

Belgium, as one of a number of countries seeking the general's extradition, should also have the chance to have a Belgian doctor present at a further medical examination of the general.

These steps should be taken before Mr Straw makes a final decision, Mr Stein said. "We say his approach, in the absence of that, is flawed."

Concern

Mr Straw has said he will not make a final decision until the judicial proceedings launched in the courts are completed.

The challenge in the High Court by the human right's groups is being made on three grounds - the general procedures used by the home secretary to reach his decision were not fair; failure to disclose details of the medical reports meant parties were not able to challenge the findings; and concern over the choice of experts to conduct the medical tests on the general.

In particular, there was concern that an old-age psychiatrist was not involved in the tests which were conducted earlier this month, and which Mr Straw said "unequivocally and unambiguously" found that the 84-year-old former dictator was unfit to stand trial.

General Pinochet has been fighting extradition to Spain since he was detained in London more than a year ago.

Belgium was one of three countries, along with France and Switzerland, which filed extradition bids in the wake of the Spanish request.

A Chilean air force plane is waiting on a runway in Bermuda, preparing to fly General Pinochet home from the UK if he is released.