ISLAMABAD (AFP) - Pakistan's embattled former military ruler Pervez Musharraf flew to Karachi on Saturday to undergo medical tests, according to close aides, two days before he is due to appear in court in Islamabad.

It is the first time that the former president, who will be staying with his daughter in Karachi, has left Islamabad after being indicted in a high treason case by a special court last month.

Musharraf is due to appear in court in person in Islamabad on Monday in the murder case of a slain Baluch nationalist leader, or face arrest. But his aides insisted his visit to Karachi had been pre-planned.

"He was planning to spend some time with his daughter there as his wife is in Dubai taking care of his ailing mother," Ms Afshan Adil, a close aide and lawyer told AFP. "He is also supposed to undergo some diagnostic tests in a navy-run hospital there," she added.

It was unclear whether Musharraf would return to the federal capital for the Monday court hearing.

Musharraf left his heavily guarded farm house in Islamabad around 7pm on Saturday evening.

Two armoured vehicles escorted him to the airport, with surrounding roads closed to the public and a heavy contingent of rangers and police deployed along the route.

An AFP photographer at Islamabad airport said rangers had taken control of the area and the VVIP lounge evacuated before Musharraf's arrival.

Ms Asia Ishaq, an official of Musharraf's All Pakistan Muslim League (APML) said the visit was planned "weeks before" and that a house in the affluent neighbourhood of Clifton had been arranged.

"But he might stay at the Naval hospital depending on security," she said.

An AFP correspondent said armoured vehicles and rangers were being deployed outside the Naval hospital in Karachi.

After his indictment for treason in March, Musharraf asked to be allowed to visit his mother, who is in her 90s, in the United Arab Emirates.

But he was denied permission to leave the country due to the cases pending against him.

The treason charges relate to Musharraf's 2007 imposition of emergency rule, shortly before the Supreme Court was due to rule on the legality of his re-election as president.

He then arrested and sacked the country's top judges, including the chief justice, who challenged his decision.

The former general, who seized power in 1999 and resigned in 2008, has pleaded "not guilty" to the treason charges.

Musharraf is also on bail in three other major cases linked to his time in power.

Earlier this month, a Pakistani court hearing the murder case of Baluch nationalist leader Nawab Akbar Bugti ordered Musharraf to appear in person on April 21 or face arrest.

Mr Bugti, who was killed in a military operation, led an armed campaign to press for provincial autonomy and a greater share of profits from Baluchistan's natural resources.

Musharraf came to power in a bloodless coup in 1999, deposing then-prime minister Nawaz Sharif, who won re-election in 2013 when Pakistan underwent the first civilian handover of power since its independence from Britain in 1947.

Facing impeachment following elections in 2008, Musharraf resigned as president, going into self-imposed exile in Dubai. He returned to Pakistan in March last year on an ill-fated mission to run in the general election.

He was barred from taking part and has since faced a barrage of legal cases.