The start of former Pakistani president Pervez Musharraf's trial for treason was delayed over security fears on Tuesday after explosives were found near the road he was to take to court.

The 70-year-old had been expected to appear in person before a specially convened court in the capital Islamabad, after legal efforts failed to have the tribunal ruled invalid.

The allegations relate to his imposition of emergency rule in November 2007. Musharraf and his legal team have said the case was politically motivated.

As the court was preparing for Tuesday's preliminary hearing in the case, police said they found 5 kg of explosive material along with a detonator and two pistols close to the route Musharraf was due to take from his house to the court in Islamabad.

Muhammad Asjad, the police chief for Chak Shahzad, where Musharraf lives, said the material had not been assembled into a bomb.

After the discovery, Musharraf's lawyer Anwar Mansoor Khan told the court that the former general would not be able to attend because of serious security threats to his life.

Justice Faisal Arab, heading the bench, said he understood the "gravity" of Musharraf's situation and asked his lawyers to file an application to exempt him from appearing in person.

The court was expected to decide later on Tuesday whether to continue the hearing to a later date or to proceed in Musharraf's absence.

The team of 10 lawyers representing Musharraf has also filed petitions challenging the authority of the special court and objecting to the appointment of the prosecutor.

Security around the court was tight for the man who led Pakistan into its uneasy alliance with the US in the "war on terror" and now lives under heavy armed guard because of Taliban threats to his life.

AFP-AP