Chancellor Gordon Brown has flown into Afghanistan for a surprise visit to British troops.
Mr Brown arrived in Kandahar, accompanied by Defence Secretary Des Browne, before going on to meet both UK military commanders and local political leaders.
He was also scheduled to talk informally to just some of the 6,300 soldiers Britain has based in Afghanistan, mainly around the lawless Helmand province.
The Chancellor announced an extra £400 million for military operations in Iraq and Afghanistan in his Budget earlier this month.
This is his first visit to the country and a Treasury source said: "The main reason for the visit is to see British troops, hear about their experiences and see their equipment, taking an opportunity to see on the ground the results of the investment that has gone in over the past 12 months.
"The Chancellor will also be talking to local political leaders about helping economic development in Afghanistan."
The Chancellor told reporters travelling with him: "One of the things I will be saying to the forces I meet is you become ever more aware of the risks and dangers they are having to undergo and the courage and the bravery of the troops themselves."
Of the British personnel held in Iran, the Chancellor said: "Overnight, the UN resolution is calling definitively for their release. That's the unanimous view of the international community.
"The treatment of Faye Turney is cruel, callous, inhuman and unacceptable."
Mr Brown will announce a further £15 million in aid to Afghanistan, to be spent on so-called "quick impact projects", such as developing village wells and water supplies.
