Pakistan publicly acknowledged for the first time Thursday that last year's attack on Mumbai was largely planned on its soil and that it had arrested most of the key plotters.

Pakistan's Interior Ministry chief Rehman Malik spoke during a press conference in Islamabad, saying Thursday that it had arrested most of the chief suspects including one described as the main operator.

Malik has started criminal proceedings against eight suspects but he reiterated that authorities needed more evidence from New Delhi to secure convictions.

Some part of the conspiracy has taken place in Pakistan, Mr. Malik told reporters. As for the plotters, most of them are in our custody.

Eight people have been charged in Pakistan with abetting, conspiracy and facilitation of a terrorist act, and six of them are currently in Pakistani custody, Mr. Malik said. The suspects being held by Pakistan include at least one Pakistani who was recently residing in the Spanish city of Barcelona, he said.

Malik added that some of the plotters were linked to the banned Pakistani Islamic militant group Lashkar-e-Taiba, the outfit that U.S. and Indian officials say was behind the attack, which left at least 170 people dead.

India's Foreign Ministry called Pakistan's announcement a positive development and said it would consider Islamabad's request for further information.

Among the information being sought are DNA samples from sole attacker captured by India, Mohammed Ajmal Kasab, and the nine others slain by Indian security forces. Mr. Malik said Pakistan needs the samples to confirm their identities.

While Mr. Malik offered few revelations Thursday, his statement was a clear sign that Pakistan intends to cooperate with international efforts to try and convict those behind the attacks, as India and the U.S. have demanded.

I want to assure the international community, I want to assure all those who have been victims of terrorism that we mean business, Malik said, waving a copy of Pakistan's initial findings at reporters gathered inside his ministry.

We will continue our investigation, but we want tenable evidence from India. We want full cooperation from India so that this kind of ring be smashed.

There had been doubts about Pakistan's commitment in recent weeks, with some officials suggesting that attack was planned outside the country and that Pakistanis played only an incidental role in the entire operation.