UK prime minister Gordon Brown has travelled to India to discuss terrorism and try to calm relations with Pakistan following the Mumbai attacks.
He met the Indian Prime Minister Manmohan Singh to discuss the aftermath of the attacks which killed at least 170 people, including one Briton.
India has announced a security overhaul after the attacks which it blames on Pakistan-based militants.
Mr Brown later flies to Pakistan for talks with President Asif Ali Zardari.
India has urged Pakistan to take action over the attacks.
Pakistan denies any involvement, but has promised to co-operate with the Indian investigation.
President Zardari pledged to take "strong action" against terrorists.
But he has also called on India to share more information about the attacks.
Speaking during his surprise visit to Afghanistan on Saturday, Mr Brown said he also hoped to raise the issue with Mr Zardari.
He described Pakistan's border region with the country, where he met troops fighting the Taleban, as one end of a "chain of terror" that could stretch to Britain if more was not done to tackle the threat of al-Qaeda.
The prime minister's visit to Afghanistan came a day after four Royal Marines were killed in two separate bomb attacks.
Mr Brown spoke of his "disgust and horror" at the willingness of the Taleban to use a 13-year-old child to deliver a bomb in a wheelbarrow to a Marine patrol, killing three men and the young boy.
The PM is expected to update MPs on the security situation in Afghanistan in an oral statement to the House of Commons on Monday.
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