On Tuesday, a suicide bomber blew himself up at a rally where hundreds had gathered to hear Pakistan's suspended top judge speak, killing 15 people and plunging the country further into crisis.

The clashes in the North Waziristan tribal region came as President Pervez Musharraf said Pakistan was in "direct confrontation" with extremists who have launched a wave of attacks since a government raid on an Islamabad mosque.

In the first attack, insurgents fired rockets at a military convoy and then opened fire with automatic weapons near the village of Lwara Mundi, chief military spokesman Major General Waheed Arshad said.

"Seventeen soldiers were martyred and more than a dozen miscreants were also killed when troops returned fire," Arshad told AFP.

"Initial reports say that the fighting was heavy," a senior security official based in the area said.

The mountainous area where the ambush took place is near where Pakistani forces earlier this year erected the first 35-kilometre (20-mile) stretch of a controversial anti-Taliban fence along the border with Afghanistan.

About six hours later another clash erupted after militants attacked troops in Mir Ali, about 50 kilometres away in the same region. Five rebels were killed and there were no military casualties, Arshad said.

In other violence overnight a roadside bomb blast in North Waziristan injured six civilians and a soldier.

Separately a landmine exploded overnight outside the home of politician Mohammad Ajmal Khan, who served as federal sports minister in the 1990s, in Miranshah, the main town in the tribal area.

The blast destroyed his front gate but caused no casualties, officials said.

Pro-Taliban militants in North Waziristan on Sunday tore up a controversial 10-month-old peace deal with the government, further fuelling tensions after last week's assault on the radical Red Mosque in Islamabad.

SUICIDE ATTACK KILLS 15

A suicide bomber blew himself up on Tuesday at a rally where hundreds had gathered to hear Pakistan's suspended top judge speak, killing 15 people and plunging the country further into crisis.

The attack in Islamabad ramped up the pressure on President Pervez Musharraf on two fronts -- his suspension of chief justice Iftikhar Muhammad Chaudhry and a wave of violence that has followed the storming of the radical Red Mosque.

The powerful blast splattered human remains outside a marquee decorated with balloons ahead of the rally in support of Chaudhry, who was not present at the time. He arrived later and joined lawyers in prayer for the victims.

Hospital officials said 15 people were killed in the bombing, including two women, and 43 injured, five of them police. Many of the injured had their clothes ripped off by the explosion and suffered horrific burns.

"I saw with my own eyes bodies being ripped apart and hands and arms flying through the air," Shafqat Hayat, chief legal advisor to cricketer-turned politician Imran Khan, told AFP at the scene.

"It is now clear that it was a suicide attack," Deputy Information Minister Tariq Azeem said. He told a private television station he could not rule out that the attack was in revenge for the Red Mosque raid.

The assault on the pro-Taliban mosque compound last week killed 11 soldiers and 75 people inside the compound, mainly militants.

The site of the blast, around 100 metres from the stage where Chaudhry was to speak, was littered with dozens of shoes as well as the mangled remains of chairs and a motorcycle.

The rally, arranged by local lawyers, was the latest in a series around the country which have drawn tens of thousands of lawyers and opposition activists in support of Chaudhry since his ouster by Musharraf on March 9.

"We deeply regret the loss of life. The lawyers will not be stopped in their peaceful movement," Chaudhry's main lawyer Aitzaz Ahsan told reporters as the judge arrived and prayed inside the marquee.

The president of the Supreme Court Bar Association, Munir Malik, said it was an "attack on the chief justice by the agencies" -- the term used by Pakistanis to refer to the country's powerful intelligence agencies.

But there was also speculation that the attack targeted workers from the Pakistan People's Party (PPP) of former prime minister Benazir Bhutto, as it happened next to a stall for the leading opposition party's workers.

Bhutto, who lives in exile in Dubai and London, recently backed Musharraf's action against the Red Mosque. She told local TV that some people believed the attack was "the militants' response to the PPP's firm stand against extremism."

No one claimed responsibility for the blast.

A string of suicide attacks in northwest Pakistan have killed more than 75 people, apparently in retaliation for the storming of the Red Mosque.

A suicide bomber hit a checkpost in the tribal region of North Waziristan earlier Tuesday, killing three soldiers and a civilian, the army said.

Meanwhile the Supreme Court is expected to decide within days whether to allow or overturn Chaudhry's suspension on charges of misconduct.

Chaudhry's defenders say he was ousted because he may have stood in the way of Musharraf's bid to get re-elected by the outgoing parliament this year as president while also staying on as army chief, in defiance of the constitution.

Chaudhry has denied the charges and challenged his suspension.