A suicide bomber blew himself up Tuesday among hundreds of lawyers at a rally in Pakistan's capital, killing at least 12 people and wounding at least 40 more in one of two deadly bombings of the day.

The blast in Islamabad occurred as former chief justice Iftikhar Mohammed Chaudhry, who was suspended by the government, was on his way to attend the rally.

Chaudhry was five kilometres from the scene when the bomb exploded near the stage set up for him. Many of the dead and injured were lawyers who had attended the rally to hear Chaudhry.

Meanwhile, in Pakistan's volatile northwest, which shares a porous border with Afghanistan, a suicide bomber struck at a security post, killing three soldiers as well as a bystander.

No group has claimed responsibility for either of the attacks and there was no indication who may have carried them out.

There has been a surge in violence by Islamic extremists enraged by Pakistani President Gen. Pervez Musharraf's decision to order troops to storm Islamabad's radical Red Mosque this month.

Interior Ministry spokesman Javed Iqbal Cheema said there was a "possibility" that the attack in the northwest was a response to raid of the Red Mosque, where Islamic radicals and students were locked in a standoff with soldiers. The radicals were accused of trying to impose a Taliban-style rule of law in Islamabad.

Since the conflict at the Red Mosque began on July 3, at least 108 people have died in suicide attacks and bombings across the northwest. Seventy-five soldiers and police were among the victims.

With files from the Associated Press