India says there is evidence that foreign militants were involved in Saturday's bomb attacks in Delhi, in which at least 62 people died.
India has not publicly blamed any group for the attacks
Prime Minister Manmohan Singh told Pakistani President Pervez Musharraf that he expected Pakistan to honour its promise to end cross-border terrorism.
The BBC's Sanjoy Majumder says India believes groups based in Pakistan or linked to them may have been involved.
Pakistan says it has no indication that Pakistani groups were involved.
A little-known Kashmiri group said it was behind the attacks.
Police say they are trying to verify the claim by Islami Inqilabi Mahaz.
Gen Musharraf has condemned the bombings and offered Pakistan's support to the Indian investigation.
Mr Singh made the comments during a telephone call in which Gen Musharraf offered his condolences for the triple bombings, which happened in quick succession.
According to an Indian Foreign Ministry statement, Mr Singh told Gen Musharraf said he "continued to be disturbed and dismayed at indications of external linkages of terrorist groups with the 29 October bombing".
DELHI BOMB SITES
Paharganj: 16 die near train station at 1745 (1315 GMT)
Sarojini Nagar: 43 killed, minutes after Paharganj attack
Govindpuri: Bus driver throws bomb from vehicle - no deaths
Figures from Sunday
He then "drew the president's attention to Pakistan's commitment to ending cross-border terrorism".
A Pakistani foreign ministry spokeswoman said the government had no indication that Pakistani groups had been involved in the attacks.
"Unless they share the evidence with us, it remains a mere claim which we cannot accept," she said.
India and Pakistan have been involved in a long-running dispute over the territory of Kashmir.
Earlier on Monday, Gen Musharraf said this month's devastating earthquake in Pakistan and India provided an opportunity to help the two countries resolve their dispute.
On Sunday, the two countries opened several points along Kashmir's line of control - the de facto border between the two countries - to provide better access for relief workers to earthquake victims.