"They will be handed over to Indian authorities on Friday," said Faqir Mohammad Jadam Mangrio, an adviser to the Sindh provincial government said on Thursday.

Mangrio said the fishermen would be handed over at the Wagah border crossing in eastern Pakistan.

Twenty of the fishermen were in their teens when they were detained, he said. They had been kept at a separate children's detention facility in Karachi.

The Indian authorities were due to release 31 Pakistani fishermen, he said.

The authorities from the old rivals frequently arrest each other's fishermen for intruding into territorial waters in the Arabian Sea.

Friday's repatriation will be the fourth in recent years. Pakistan has detained a total of 621 Indian fishermen since September 2005. India has detained at least 60 Pakistani fishermen during the same period, Mangrio said.

Fishermen complain they often do not know whose waters they are in because of the dispute over the maritime boundary.

Indian and Pakistani officials are due to begin two days of talks in the Pakistani city of Rawalpindi on Friday aimed at working out a mechanism for a joint survey of the Sir creek.

The boundary talks are part of a tentative peace process the nuclear-armed neighbours launched in early 2004.