Pakistan said an outlawed terrorist group believed to be linked to al-Qaeda was behind the bombing of the Marriot hotel in Islamabad in September.

Rehman Malik, Pakistan's Interior Minister, told the country's National Assembly that Lashkar-e-Jhangvi had played a part in organising the attack, in which a truck packed with 600kg of explosives rammed the gates of the luxury hotel, killing more than 50 people, including the Czech ambassador and two US Marines.

Experts said that the attack, on a building just a few blocks from Pakistan's Parliament, underscored both the growing reach of al-Qaeda and affiliated groups in Pakistan and the new-found confidence with which they operate in the country. Al-Qaeda and other militant groups now seem to be operating in Pakistan's capital and other major cities with impunity, security analysts said.

Mr Malik said that the truck was loaded with explosives in the town of Jhang in Punjab province, south of the capital Islamabad. He said the plot was "assisted" by Lashkar-e-Jhangvi, a Sunni Muslim militant group accused of killing hundreds of minority Shiites across Pakistan.

The move came as India urged Pakistan to take urgent action to hunt down the terrorist network responsible for last month's attacks on Mumbai. India is convinced that the Pakistan-based militant group Lashkar-e-Taiba (LeT), also thought to have links to al-Qaeda, was behind the assault, which left more than 170 people dead.

Pakistan officials have so far denied Indian claims that they have been handed proof that the ten gunmen who attacked Mumbai were from Pakistan.

The Indian Foreign Minister Pranab Mukherjee said this week: "Pakistan's response so far has demonstrated their earlier tendency to resort to a policy of denial and to seek to deflect and shift the blame and responsibility." He also called on the United States and United Kingdom to place more pressure on Pakistan.

However, the identification of Lashkar-e-Jhangvi as a playing a part in the Marriot blast may indicate the scale and complexity of the terrorist threat that confronts Pakistan's recently elected government.

Authorities in Pakistan recently claimed to have cracked a terrorist network set up under which Lashkar-e-Jhangvi operatives had been directed by Ahmad Omar Saeed Sheikh, the jailed killer of American journalist Daniel Pearl, to assassinate President Musharraf either in Rawalpindi or in Karachi, according to the Press Trust of India.

Sheikh was released by India along with Jaish-e-Mohammad chief Maulana Masood Azhar and another terrorist in exchange for passengers on an Indian Airlines flight hijacked in 1999.

Previously, Mr Malik, Pakistan's Interior Minister, had appeared to blame Tehrik Taleban Pakistan, an outlawed militant group operating from a lawless tribal region in the north, for the Marriot blast. The group is also said to be closely linked with al-Qaeda. Many other Pakistani militant groups have mutated into small cells after being banned and work as an extension of al-Qaeda.

The Marriot attack came as Pakistani forces stepped up operation against the militants in Bajaur tribal region considered al-Qaeda's operational base. Many observers believe the Marriot attack was a retaliation to the military offensive. The fighting there, the most intense since Pakistan allied itself with the United States in its War on Terror in 2001, has claimed hundreds of lives.

Al-Qaeda and their allies among tribal militants had repeatedly threatened to escalate the conflict if that military operation was not stopped. Anti-American sentiments are also high in the country after surge in US predator attacks against suspected militant hideouts inside the Pakistani tribal region.

Pakistan has arrested at least two people in connection to the September 20 Marriot blast, but no one has been formally charged.

A previously unknown group called the Fidayeen-e-Islam had claimed responsibility for the assault and warned of more such attacks on foreigners.

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