Lakhvi is allegedly a member of Lashkar-e-Taiba, a banned group blamed for other attacks on its soil. Analysts say it was created in the 1980s by Pakistan's intelligence agencies to act as a proxy fighting force in Indian Kashmir.
Many analysts suspect elements within Pakistan's intelligence agencies keep some links with Lashkar and other militants, either to use against India or in neighboring Afghanistan, but U.S.
counterterrorism officials say there is no evidence linking Pakistan state agencies to the Mumbai attacks.
The United States says Lashkar is linked to al-Qaida. In May, the U.S. blocked the assets of Lakhvi and three other alleged members of the group, including its leader, Hafiz Mohammed Saeed.
Indian officials in New Delhi and Islamabad were not available for comment.
State Department spokesman Sean McCormack did not confirm Lakhvi's arrest, but said the reported raid was a "positive step."
India says the 10 gunmen who killed 171 people in the country's financial hub on Nov. 26-29 were Pakistani members of Lashkar-e-Taiba. Washington said Sunday the attack was planned in Pakistan.
India and Pakistan have fought three wars since 1947, but their ties had been improving in recent years. U.S. officials fear a serious disruption would dent its hopes for regional stability needed to better fight al-Qaida along the Afghan border.
Backed by a helicopter, the troops grabbed Lakhvi and at least 11 other suspected militants Sunday in a raid on the riverbank camp run by Lashkar-e-Taiba, two officials said.
Before the militants were subdued, there was a brief gunfight that wounded several extremists, said the officials from the government and the intelligence agency. Both spoke on condition of anonymity because of the sensitivity of the subject.
People living near the camp heard several loud explosions, but reporters Monday were prevented from traveling to the scene close to the capital of Pakistani Kashmir, Muzaffarabad.
Indian officials say the sole Mumbai attacker captured alive has told them that Lakhvi recruited him for the mission and that Lakhvi and another militant, Yusuf Muzammil, planned the operation.
Pakistan banned the group in 2002 following U.S. pressure, but there have been few if any convictions of its members. An Islamist charity called Jemaat-ud-Dawa sprang up after the ban, which U.S. officials say is a front for the group.
Jemaat-ud-Dawa - which denies any link to Lashkar - runs a chain of schools and clinics throughout the country and has helped survivors of two deadly earthquakes in recent years.
Moving against that network amid pressure from the U.S. and traditional rival India risks igniting Muslim anger that could destabilize the county's shaky, secular government.
The U.S. Treasury Department alleged that Lakhvi directed Lashkar-e-Taiba operations in Chechnya, Bosnia and Southeast Asia and in 2004 allegedly sent operatives and funds to attack U.S. forces in Iraq.
Pakistani authorities did not formally announce the arrest of Lakhvi, which is common here, especially in sensitive cases.
Officials would not speculate on what the country planned to do with him.
India has indicated it wants suspects in the Mumbai attacks transferred to its custody, but Pakistani President Asif Ali Zardari said last week anyone arrested in the country would be tried in Pakistani courts.
Observers say that handing over suspects to India is unlikely because it could provoke a backlash by Muslim and nationalist hard-liners already angered by Pakistan's pledge to cooperate with New Delhi.
The military released a brief statement late Monday saying intelligence-led operations on banned militant groups were under way and that arrests had been made. The statement gave no more details and it was not clear if the operations included Sunday's raid.
The government also said it was investigating allegations "concerning the involvement of any individual or entity in Pakistan" in the Mumbai attacks.
It said it needed more evidence from India to continue the investigation and proposed a "high-level delegation from Pakistan may visit New Delhi as soon as possible."
Two of Pakistan's wars with India were fought over Kashmir. In 2001, an attack by suspected Lashkar-e-Taiba militants on the parliament building in New Delhi brought the countries close to a fourth conflict.
The Mumbai attacks came as India was preparing for national elections in spring. Opposition parties, including the hard-line Hindu nationalist Bharatiya Janata Party, hope to make gains amid anger at alleged security lapses before the attacks.
But the ruling Congress party won two state elections Monday, including in the capital New Delhi, and was leading in a third, election officials said, in an early sign that opposition charges were not sticking.
Tensions with India have led to fears Pakistan's military may withdraw troops from the border with Afghanistan to reinforce its frontier with India, a highly worrying scenario for the United States and other Western allies.
Pakistani troops in the lawless frontier region are battling militants blamed for rising attacks in Afghanistan, while U.S.
officials fear al-Qaida leaders are regrouping there, possibly plotting attacks on the West.
Much of the supplies for U.S. and NATO troops to Afghanistan must first pass through northwestern Pakistan, where they are increasingly being targeted by militants.
Early Monday, militants in the northwestern city of Peshawar attacked a terminal for supply trucks for the second day running, torching scores of military vehicles awaiting shipment, a witness and an Associated Press reporter said.
No one was hurt, but it showed the vulnerability of the supply line as well as the increasing lawlessness of Peshawar, where a U.S. aid worker was gunned down last month.
NATO officials say the attacks on the supply line do not affect their operations in Afghanistan, but acknowledge they are looking for other supply routes.
