Qari Saifullah Akhtar - a top extremist leader accused by Ms Bhutto of plotting against her in a book published after her assassination in December - was seized on Monday, interior minister Hamid Nawaz said.

'Most probably he is involved in the attack in Karsaz on Benazir Bhutto's rally. He is a big character,' Mr Nawaz said, referring to the October attack on Ms Bhutto's homecoming parade in Karachi's Karsaz district that killed 139 people.

Two-time premier Ms Bhutto was unharmed in that attack, but was killed two months later in another assassination attempt, in Rawalpindi at an election rally.

Seized with his three sons
Akhtar was seized with his three sons, Mr Nawaz added.

Akhtar was the one-time head of Harkat Jihad-e-Islami, the main Pakistan support group for Afghanistan's extremist Taleban movement, and he spent most of his time before 2004 living in Afghanistan, and met bin Laden several times.

He was arrested in the United Arab Emirates in August 2004 and later extradited to Pakistan, where he was released under unclear circumstances.

An official in Punjab province said that Akhtar was recently engaged in a brawl with a rival jihadi group over the occupation of a shrine there, and said the arrest was likely linked to the dispute, not the attack on Ms Bhutto.

Ms Bhutto's assassination on Dec 27 overshadowed elections held on Feb 18, which saw her Pakistan People's Party (PPP) trounce President Pervez Musharraf's political allies, but a fresh wave of violence has followed the polls.

In the latest attack, the Pakistan army's top medical officer was among eight people killed in a suicide bombing on Monday in the garrison city of Rawalpindi.

Lieutenant General Mushtaq Baig, the army's surgeon general, was the most senior Pakistani military official to be assassinated since Mr Musharraf joined the US-led 'war on terror' in 2001.

Pakistan's military said the brazen attack was likely in retaliation for operations against Islamic militants near the Afghan border.

'I think apparently it is in response and reaction to the Pakistan army's operations against militants in South Waziristan and other places in FATA (the Federally Administered Tribal Areas),' chief military spokesman Major General Athar Abbas said.

Pakistan has lost about 1,000 troops in operations against Taleban and Al-Qaeda militants who have built safe havens in the lawless tribal areas in the wake of the Sept 11, 2001 attacks on the United States.

Suicide attacks blamed on tribal militants, especially Baitullah Mehsud, a Taleban commander with links to Al-Qaeda who is based in South Waziristan, have soared since the start of 2007.

Rawalpindi - the site of army headquarters - has experienced eight attacks since July, claiming 88 lives including Ms Bhutto.

The latest attacks have posed an immediate challenge to Pakistan's incoming government, set to be a coalition between the PPP and the grouping of former premier Nawaz Sharif.

A spokesman for Mehsud said on Sunday that the militants were ready for peace talks with the new government, but only if it does not pursue Mr Musharraf's involvement in the 'war on terror'.

Pakistan has veered between making peace deals with militants and launching major offensives in the five years since full-scale operations started in the tribal areas in early 2003.

Neither policy has worked and the bloodshed last year spread further, from the semi-autonomous tribal belt into the country's 'settled' northwestern regions.

Elsewhere in the tribal belt a member of Ms Bhutto's party was wounded by a roadside bomb on Tuesday, just over a week after a suicide attack on one of his election rallies killed 47 people. -- AFP