Brown flew in the night of December 12 and slept at military quarters at the Kandahar air base, a spokesman in his office said.

On December 13, Brown talked with Afghan President Hamid Karzai, who flew to Kandahar. Brown also met with troops, was debriefed by army leaders, and inspected new military equipment.

The Taliban rose to power in Kandahar province before it was toppled by US-led forces in late 2001. However, the militant group has resurged in recent years, and coalition troops have been fighting ever since to contain the threat.

Brown's unannounced visit follows the British government's pledge of 500 extra troops to complement President Obama's decision to send 3,000 additional American troops.

More than 9,000 British troops are stationed in southern Afghanistan, primarily in Helmand province. It has been a militant stronghold and a poppy-growing region that helps fund the insurgency, analysts say. It supplies 90 percent of the world's opium, which is used in the production of heroin.