ISLAMABAD, Pakistan — Pakistan acknowledged for the first time on Thursday that parts of the Mumbai terrorist attacks were planned on its soil and said that six suspects were being held and awaiting prosecution.

The admission amounted to a significant about-face for the Pakistani government, which has long denied that any terrorist attacks against India, its longtime enemy, have originated in Pakistan.

Officials said as recently as Monday that they did not have enough evidence to link the Mumbai assault to Pakistan, and there have been signs of internal tensions in Pakistan over cracking down on Lashkar-e-Taiba, the Pakistan-based militant group that India and the United States have deemed responsible for the Nov. 26 attack on India’s financial capital.

Pakistani officials did not explicitly name Lashkar as the organizer of the attacks on Thursday, but they did single out as suspects two people who are known to be connected to the group.

The formal acknowledgment of a Pakistani role came on the final day of a visit to the country by Richard C. Holbrooke, President Obama’s special envoy to the region, who raised the issue with top Pakistani government officials, according to an official familiar with the conversations.

Though Pakistani officials denied the announcement was linked to Mr. Holbrooke’s visit, the Obama administration has made clear that lowering hostilities between India and Pakistan is a crucial part of a regional solution to the war in Afghanistan.

India called Pakistan’s admission a “positive development,” but said that Pakistan must still take steps to dismantle the “infrastructure of terrorism.” In Washington, the State Department spokesman, Robert A. Wood, said, “I think it shows that Pakistan is serious about doing what it can to deal with the people that may have perpetrated these attacks.”

Both India and the United States have put strong pressure on Pakistan for some concession regarding the Mumbai attacks, which American officials feared were distracting Pakistan from the task of battling militants from the Taliban and Al Qaeda who have bases inside Pakistani territory.

Despite seemingly overwhelming evidence presented by India, with the help of American and British investigators, top Pakistani officials had repeatedly raised doubts about the identity of the attackers and the links to Pakistan-based militant leaders.

Finally, on Thursday, as Mr. Holbrooke left Pakistan for Afghanistan, Rehman Malik, the senior security official in the Interior Ministry, gave the fullest public account so far of Pakistan’s investigation.

“Some part of the conspiracy has taken place in Pakistan,” he said in a televised news briefing. He emphasized Pakistan’s commitment to prosecuting the attackers and, unusually for a government official here, expressed solidarity with India.

But he was also careful to diffuse blame for the attacks, noting that the tools used by the attackers to organize their plot — cellphone SIM cards, Internet servers — provided links to other countries, however ancillary.

“We have gone the extra mile in conducting an investigation on the basis of information provided by India, and we have proved that we are with the Indian people,” Mr. Malik said.

“According to the initial inquiry report a part of the conspiracy of Mumbai attacks was hatched in Pakistan; however links have been found in other states, including the U.S.A., Austria, Spain, Italy and Russia,” he added.

A State Department official, who spoke on condition of anonymity because of diplomatic sensitivities, called the Pakistani announcement a “political decision” to ease tensions with India.

While saying they did not have enough proof that the perpetrators were Pakistanis, President Asif Ali Zardari and other civilian leaders have expressed a determination to get to the bottom of the Mumbai attacks.

Mr. Zardari even offered to send the nation’s top intelligence official to India after the attacks occurred. But his outreach to India met strong resistance from Pakistan’s powerful intelligence agency and the military.

A Defense Department official, who did not want to be named for similar reasons, said the Pakistani decision may have been an effort by the civilian government to “poke a stick” at the Pakistani military and intelligence service, which helped set up Lashkar in the 1980s as a proxy force to challenge India’s control of Kashmir, the disputed border region.

Indian officials have previously blamed Lashkar for an attack in 2000 on the Red Fort in New Delhi, as well as involvement in an attack on the Indian Parliament in 2001. Pakistan never acknowledged any Lashkar role in those attacks. The group is officially banned, though it has continued to operate openly.