WASHINGTON, US - The United States imposed sanctions Wednesday on an Al-Qaeda backer and three leaders of Pakistan-based Islamist group Laskhar-e-Taiba, which was blamed over last year's Mumbai attacks.

The US Treasury said it was imposing an assets freeze on the four, identified as Fazeel-a-Tul Shaykh Abu Mohammed Ameen al-Peshawari, Arif Qasmani, Mohammed Yahya Mujahid and Nasir Javaid.

Peshawari allegedly provided assistance, including funding and recruits, to Al-Qaeda and the Taliban militia fighting to regain control of Afghanistan and battling government forces in Pakistan.

Qasmani is said to be the chief coordinator for Laskhar and Mujahid the head of the group's media department while Javaid had served as its commander in Pakistan.

Laskhar is widely thought to have been behind last November's 60-hour bloodbath in India's Mumbai city which led to 166 deaths.

The US Treasury said its action came two days after Peshawari, Qasmani and Mujahid were added to a UN blacklist of individuals and entities linked with Osama bin Laden's Al-Qaeda and the Taliban.

All UN member states are obligated to freeze the funds and other assets of listed individuals and entities included on the blacklist, and to apply other sanctions, such as travel ban and arms embargo, a Treasury statement said.

Qasmani was also linked in the Treasury statement to the July 2006 train bombing in Mumbai that killed 186 people and the February 2007 Samjota Express bombing in India's Panipat city which killed 68 people.

He allegedly conducted fundraising activities on behalf of Lashkar in 2005 and utilized money that he received from an alleged Indian crime figure and terrorist supporter Dawood Ibrahim to facilitate the July 2006 train bombing.

But the head of one of Pakistan's biggest charities -- widely viewed as a front for LeT -- condemned the sanctions and charged that the men were welfare workers rather than members of the militant group.

"None of the four belonged to Lashkar-e-Taiba. They are welfare workers in Jamaat-ud-Dawa. None of them have a bank account in the USA or any country abroad," the head of the Dawa charity, Hafiz Mohammad Saeed, told AFP.

"The USA has never produced any proof about the involvement of Dawa in terrorism. We are a private NGO working to promote education, medical cover for the poor and need, and rehabilitation in calamity-hit areas," he added.

President Barack Obama's administration has been piling pressure on Pakistan to bring those guilty of last year's Mumbai attacks to justice, a senior US diplomat said recently.

India blames neighboring Pakistan for harbouring those who planned the attacks, and one Pakistani national is on trial in Mumbai accused of being the only gunman who survived. --AFP