New Delhi/Islamabad - British Prime Minister Gordon Brown will make an unscheduled visit to India and Pakistan as ties between the nuclear-armed neighbours came under severe strain following the terrorist attacks in Mumbai, officials said Saturday.

Brown will hold talks Sunday with his Indian counterpart Manmohan Singh, during which New Delhi is expected to share evidence about the alleged involvement of Pakistan-based militants in the attacks.

"British Premier Brown will arrive Saturday night and will have his main meeting with Prime Minister Singh on Sunday morning," an official in India's External Affairs Ministry said.

"They will discuss the situation arising out of the Mumbai attacks. Both countries will also discuss measures to step up counter-terrorism cooperation," he added.

Indian officials have blamed Pakistan-based Lashkar-e-Taiba (LeT) for masterminding the November 26 Mumbai attacks that left 173 dead, including 26 foreign nationals,
18 policemen and nine terrorists.

Local media reported that Brown's visit was not planned but he decided to travel the sub-continent to calm tensions between India and Pakistan. Another key objective, was to underscore his country's solidarity with India in the fight against terrorism.

Brown will be in Pakistan on Monday and hold meetings with President Asif Ali Zardari and Prime Minister Yousaf Raza Gilani, an official of the Foreign Ministry of Pakistan said on condition of anonymity.

Diplomatic officials in Islamabad often do not formally announce the arrival of any key figure because of security concerns.

"Pakistani leadership is expected to inform Mr Brown about the steps it has taken against the militants outfits suspected in Mumbai attacks," the official said. "At the same time he will be asked to press India to share evidence with Pakistan against these groups."

Law enforcement agencies in Pakistan have recently arrested two top militants, Zakiur Rehman Lakhvi and Zarar Shah, of LeT and banned an Islamic charity Jamaat-ud-Dawa believed to be its political front.

But Islamabad says it cannot carry out further legal proceedings against the alleged militants unless Indians do not provide concrete evidence.

Brown's visit to the region follows that of the US Secretary of State Condoleezza Rice between December 3 and 5. Russian President Dmitry Medvedev also made a planned visit to India in the first week of December.

Britain shares the US' view that any confrontation between India and Pakistan will impact the NATO-led offensive against the Taliban in Afghanistan. The situation in Afghanistan will figure prominently in the discussions, the sources told IANS news agency.

Soon after the Mumbai attacks, Brown had spoken to Singh and expressed his outrage and a "vigorous response" to the attacks. Brown said his government was ready to offer all help to New Delhi in connection with the attacks. (dpa)