Indian police said tdoay they had arrested four people over last week's suicide raid on the national parliament, blamed on Pakistan-based Kashmiri separatists.
"We have cracked the case," a senior investigating officer said. "At this time, I can only tell you that we have arrested four people, two from Delhi and two from outside."
He gave no further details but said a news conference was expected later in the day.
India has blamed the attack, in which 12 people died, on the Pakistan-based Lashkar-e-Taiba which is fighting Indian rule in the Himalayan region of Kashmir in the far north.
In a move that has raised tensions with Pakistan, India has demanded Lashkar and another Pakistan-based Kashmiri separatist group be closed, their assets frozen and their leaders arrested.
Prime Minister Mr Atal Behari Vajpayee, under pressure from his own party to send forces into Pakistani-controlled areas of Kashmir to hunt militants, said yesterday New Delhi had reached the limit of its tolerance.
Urging international pressure on Pakistan, he also hinted India, which held back from crossing the Line of Control dividing Kashmir during the India-Pakistan Kargil conflict in 1999, may not show the same restraint in future.
"We could have gone across the border during Kargil but we showed restraint," he said. "Again we are being told to show restraint. We have shown a lot of patience, but there is a limit."
Pakistan President Pervez Musharraf has threatened to retaliate with force if India took precipitous action.
"Any adventure (against Pakistan) would be met with force," he said yesterday, but pledged to act against any Pakistan-based group proven to be involved in the New Delhi raid.
The nuclear rivals have fought two of their three wars since their independence in 1947 over Kashmir.