Taliban militants hanged a teenager in southern Afghanistan because he had American money in his pocket, stuffing five U.S. $1 bills into his mouth as a warning to other villagers not to use dollars, police said Monday. Taliban militants elsewhere killed eight police.

The 15-year-old boy was hanged from a tree on Sunday in Helmand, the most violent province in the country and the world's No. 1 poppy-growing region.

"The Taliban warned villagers that they would face the same punishment if they were caught with dollars," said Wali Mohammad, the district police chief in Sangin.

Dollars are commonly used in Afghanistan alongside the afghani, the local currency, though dollars are more commonly seen in larger cities where international organizations are found.

Militants often justify their attacks and executions as a response to U.S. meddling in Afghan affairs.

The Taliban killed another man in Sangin on Saturday who had sought farm assistance and seeds from an international aid program, Mohammad said. The militants accused him of being a spy and shot him to death.

Taliban insurgents in Ghazni province, meanwhile, ambushed a police convoy on Sunday, killing eight officers, said Abdul Khaliq Nikmal, spokesman for the provincial governor.

He said Afghan authorities have sent police reinforcements to the area and are meeting with U.S. military officials to plan a counterattack.

Violence has surged in Afghanistan in recent months. Last week alone violence killed more than 270 dead, including 165 militants killed in two large battles in the south and 30 people killed in a suicide bombing on an army bus in Kabul.

President Hamid Karzai on Sunday Karzai said he would be willing to meet personally with Taliban leader Mullah Omar and factional warlord Gulbuddin Hekmatyar, leader of Hezb-i-Islami, in exchange for peace.

On Sunday, Karzai's spokesman, said there is "serious debate" among some Taliban fighters about laying down arms.

But the Taliban said international troops must first leave the country before any talks are held, a position mirrored by Hezb-i-Islami in an announcement Monday.

"Negotiations with Karzai have no worth in the presence of American forces," said Haroon Zarghun, a purported spokesman for Hezb-i-Islami.

"Karzai has, in fact, no authority in the presence of American troops. Talks would be waste of time in such a situation," he told the AP by telephone. "If the United States announces to leave Afghanistan, then we will be ready to hold talks."

Insurgency-related violence has killed more than 4,600 people so far this year, most of them insurgents, according to an AP tally of figures from Afghan and Western officials.

In Helmand's Reg district, Afghan and U.S.-led coalition forces, acting on intelligence reports, were pursuing militants hiding out in the area when they came under attack, the coalition said in a statement. The troops called in airstrikes and fought the militants in a gun battle.

More than 20 militants were killed, but there were no reports of civilians hurt. It was not immediately possible to verify the death toll independently.