Islamabad said New Delhi had not freed the expected number of Pakistanis in an exchange across the common border at Wagah on Friday while India made a similar complaint to its neighbour.

India has released 38 Pakistanis while Pakistan has freed 19 civilian prisoners under the agreement signed by the countries in May as part of a confidence-building process under an ongoing peace dialogue.

Pakistan handed over a batch of 20 Indian fishermen Saturday at Wagah after a day's delay due to the breakdown of a vehicle transporting the prisoners to the border crossing.

India's foreign ministry said in a statement Friday the number of Indian prisoners released by Pakistan fell far short of what it expected.

"We are disappointed to note that the 240 fishermen whose national status has already been confirmed were not released ... despite the understanding between the Home Secretary of India and the Interior Secretary of Pakistan," it said.

Pakistan's foreign ministry, however, said the Indians had not lived up to their commitments under the prisoner exchange accord.

"The Indians should have released the bulk of some 493 Pakistani prisoners who we think meet the release criteria set out in the May agreement," ministry spokeswoman Tasnim Aslam told AFP.

The agreement provided for the release of each other's nationals who had completed their jail terms and had their national status verified.

"In our view, a large number of Pakistani prisoners have qualified for release but the Indians claim otherwise," Aslam said.

"Both sides have to follow the same principle," she said, adding that neither side could take a selective approach.

The prisoner swap deal has been seen as one of the few successes in the slow-moving peace dialogue launched by the South Asian nuclear-armed rivals in January 2004.

The peace process has led to the restoration of full diplomatic ties and increased people-to-people contacts between the neighbours.

But the dialogue is yet to produce a breakthrough on the future of Kashmir, trigger of two of their three wars. The Himalayan region is divided between the nations and claimed in full by both.