US welcomes 'positive steps' taken by Islamabad as key suspect faces grilling.
Pakistani officials on Tuesday quizzed an alleged "key planner" of the Mumbai attacks as the United States urged further cooperation with Washington and New Delhi to prevent follow-on strikes.
As the focus in the aftermath of the carnage in India's business capital shifts to Islamabad's attempts to clamp down on militant organisations, Zaki-ur-Rehman Lakhvi faced a grilling over his role in the carnage.
Lakhvi - who according to Indian media was named by the lone surviving gunman as a key planner of last month's attacks - was detained in Pakistan's central Punjab province on Saturday.
A further 15 people were arrested in the disputed region of Kashmir a day later.
Amid the launch of an operation by the Pakistan military targeting militant groups, the United States Monday welcomed "positive steps" taken by Islamabad since the Mumbai attacks.
Pakistan President Asif Ali Zardari telephoned US Secretary of State Condoleezza Rice to brief her on actions taken by Pakistan since her visit to Islamabad and New Delhi, Rice's spokesman Sean McCormack said.
McCormack said Pakistan appeared to be taking "some positive steps" when asked to comment on news reports that Pakistan had made a major arrest.
"What we don't want to see are future attacks coming, emanating from Pakistani soil," McCormack added.
The White House also welcomed Islamabad's actions, with spokeswoman Dana Perino saying: "I think there is no doubt that Pakistan has taken some positive steps."
"It's critically important now... that we continue to work together, the Indians, the Pakistanis, the United States and our allies, to prevent follow-on attacks after the attacks in Mumbai," she said.
The strikes at the end of last month left 172 people dead, including nine gunmen, and have soured ties between the nuclear-armed neighbours which have fought three wars since independence from Britain.
India says all 10 gunmen came from Pakistan and has handed Islamabad a list of 20 terror suspects, with demands for their arrest and extradition.
The group of 15 people arrested late Sunday were at a camp run by a charity closely linked to Lashkar-e-Taiba (LeT) - the group at the centre of investigations into the Mumbai siege, an intelligence official said.
Initial reports indicated that Lakhvi was arrested in the raid on the Jamaat-ud-Dawa camp. However, a senior security official later said his arrest had taken place a day earlier.
Jamaat-ud-Dawa is run by Hafiz Saeed , who founded Lashkar-e-Taiba in 1989. He reportedly abandoned LeT when it was outlawed in Pakistan after India alleged it was behind a 2001 attack on the Indian parliament in New Delhi.
Lashkar-e-Taiba ("Army of the Pious") was established to fight Indian rule in Kashmir and has past links to both Pakistani intelligence services and Al-Qaeda.
Saeed on Monday condemned the arrests, saying the Pakistan government had shown "weakness by targeting Kashmiri organisations."
Jamaat-ud-Dawa is seen by many as the political wing of Lashkar-e-Taiba, which is on the US watchlist of terrorist organisations.
Meanwhile, US counter-terrorism and military officials are reassessing their view of Lashkar-e-Taiba and believe it a greater threat than they had previously recognised, The New York Times reported Monday.
Citing unnamed US intelligence officials, the daily said Lashkar had gained strength in recent years with the help of Pakistan's main spy service, which has allowed the group to train and raise money.
But US officials said there was no hard evidence linking Pakistan's Inter-Services Intelligence (ISI) to the Mumbai attacks, the report said.