Pakistan said today it had arrested the alleged ringleader and five other suspects behind the Mumbai terror attacks that left 179 people dead as it acknowledged for the first time that they were launched from Pakistani soil.

"Some part of the conspiracy has taken place in Pakistan," Rehman Malik, Islamabad's top interior ministry official, told reporters. "Most of them [the suspects] are in custody."

He said investigators had traced a boat used by the attackers to reach India from Pakistan and discovered two of the suspects' hideouts near the southern port city of Karachi. Other leads pointed to Europe and the US and Malik said Pakistan would ask the FBI for help.

India, which has maintained that the attack was planned and carried out by militants in Pakistan, has been pressing the Pakistani government to crack down on Lashkar-e-Taiba, a Pakistan-based militant group widely blamed for the bloodshed. Pakistan has already arrested several of its leaders.

Tracing telephone calls and bank transfers had led to the capture of a key figure in the conspiracy, Hammad Amin Sadiq, Malik said. "He was basically the main operator," Malik said, adding that his interrogation led to the raid on the two hideouts, one in Karachi, and the other two hours' drive way.

Malik said the breakthrough in the investigation came when the authorities traced the fishing boat used by the militants, and purchases of equipment such as life jackets and the engine for the rubber dinghy used by them to go ashore in Mumbai, India's financial centre.

"They had some kind of training, they went into the ocean," Malik said, saying they had sailed from Karachi. "Some of the accused who have been arrested … have given us the full rundown."

Malik said investigators had been unable to establish the identities of the nine gunmen killed in the attack last November, although Pakistan has confirmed that Mohammad Ajmal Kasab, the gunman caught alive, was a Pakistani. He added that the evidence collected made a connection to the leadership of Lashkar-e-Taiba, including Zaki-ur-Rehman Lakhvi and Zarrar Shah, who India says masterminded the attacks. The Indian foreign ministry said that the information would be studied before any reaction was given.

Pakistan released the results of its investigation as Richard Holbrooke, Barack Obama's special envoy to Pakistan and Afghanistan, finished a four-day visit to the country. Holbrooke was scheduled to arrive in Kabul today and is due to visit India next week on the final leg of a regional tour to devise a new strategy for stabilising the region.