U.S. Secretary of State Hillary Clinton is in Afghanistan for talks aimed at finding a political solution to the 10-year war.

Clinton arrived in Kabul late Wednesday on a previously unannounced visit.

U.S. officials say the secretary will meet with Afghan President Hamid Karzai and other officials on Thursday to talk about the security transition in Afghanistan and the reconciliation process.

The Afghan government's peace talks with the Taliban have stalled since last month's killing of former President Burhanuddin Rabbani, who was leading President Karzai's outreach to the insurgents as head of the High Peace Council.

A suicide bomber posing as a Taliban emissary killed Rabbani at his home in Kabul on September 20.

Violence in Afghanistan has escalated as international troops begin withdrawing from the country and transferring security responsibility to their Afghan security forces.

Afghan officials said Wednesday that five Afghan troops were killed in a roadside bomb explosion in the western province of Herat.

The officials said the troops were killed after their vehicle struck the bomb in the Pashtun Zarghun district.

An Afghan army officer and four soldiers were killed in the attack. No one has claimed responsibility for the blast.

Two NATO soldiers were also killed in a bomb attack Wednesday. The coalition said the service members were killed in eastern Afghanistan, but gave no other details.