A homicide attack on a U.S. military convoy in eastern Afghanistan killed a boy playing nearby, while a market bombing in a southern border town left two people dead in the latest violence to sweep the country.

Afghan officials also reported heavy fighting Tuesday after militants attacked a provincial security patrol in eastern Khost province near the Pakistan border. A "large number" of militants died, officials said.

An upsurge in attacks by Taliban forces this year has triggered the deadliest fighting since the militia's ouster from power in late 2001. The U.S.-led coalition has launched a major offensive in the volatile south, killing hundreds of militants in the past two months, including an estimated 70 insurgents since Monday.

CountryWatch: Afghanistan

Defense Secretary Donald H. Rumsfeld visited Afghanistan on Tuesday and discussed the worrying spike in violence with President Hamid Karzai, who stressed his country needed continued U.S. support, particularly to strengthen its weak police force.

On Wednesday, a bomb planted in a fruit cart exploded in a crowded market in the Kandahar provincial town of Spin Boldak, less than a mile from the Pakistani border. Area police chief Haji Abdul Wasay said two men were killed and eight other people wounded.

A homicide attacker in a car detonated a bomb near a U.S. military convoy 15 miles east of Khost city, killing a boy who was playing nearby and wounding three other children, said Khost provincial Gov. Merajuddin Pathan. Two American soldiers were slightly wounded in the attack, he said.

U.S.-led coalition spokeswoman in Kabul Lt. Tamara D. Lawrence confirmed there had been an explosion near a convoy in Khost but could not immediately provide further details.

The bombing follows Tuesday's clashes in Khost's mountainous border area of Shinkay in which provincial police chief Gen. Mohammed Ayub said local security forces had killed a "large number" of militants during hours of fighting.

He could not confirm intelligence reports cited by Pathan that 40 militants had died in the clashes. He said only two bodies of militants were recovered, along with assault rifles, rocket launchers and a video camera.

No security forces were hurt, Ayub said.