A roadside bomb exploded Sunday as a U.S. armored vehicle drove by in eastern Afghanistan, killing four American service members, the U.S. military said.

The armored vehicle was hit by an improvised explosive in the Pech Valley, Kunar province, where the Americans were patrolling to keep a road open to civilian and military traffic, the military said in a statement.

Earlier, a homicide car bomb exploded near the convoy of an Afghan politician leading reconciliation efforts with the Taliban militia, injuring him and killing four other people.

In addition to those attacks, Kunar Gov. Asadullah Wafa said a remote-controlled mine exploded, hitting a convoy of American troops on patrol in the Watapur area of the province, killing three and wounding one.

A U.S. military spokesman, Col. Jim Yonts, accused militants of launching "cowardly" attacks by placing bombs and detonating them from a distance.

Wafa said the explosion occurred at 4:15 p.m. as a convoy of six American vehicles was passing.

No one had been arrested and Afghan police cordoned off the area where the attack took place, Wafa said.

At least 220 members of the U.S. military have died in Afghanistan, Pakistan and Uzbekistan as a result of the U.S. invasion of Afghanistan in late 2001, according to the Defense Department.

Sibghatullah Mujaddedi, the head of the upper house of the Afghan Parliament, said the Afghan politician suffered burns to his hands and face from the blast in Afghanistan's capital, Kabul.

The two attackers and two bystanders were killed when a station wagon exploded close to Mujaddedi's vehicle, police said. Five others were hurt.

Mujaddedi accused Pakistan's Inter-Services Intelligence agency of being behind the attack, a claim Islamabad dismissed. He said Afghanistan had information that six people had entered the country to assassinate him, though he did not offer any proof.

"We have got information that ISI of Pakistan has launched a plan to kill me," Mujaddedi told a news conference hours after the attack.

"What is my fault? My fault is that I am working for the peace and prosperity of Afghanistan," he said, accusing Pakistani President Gen. Pervez Musharraf not wanting "Afghanistan to be safe and secure."

Pakistan's Foreign Ministry spokeswoman Tasnim Aslam said "Pakistan rejects the baseless allegations."

Mujaddedi's allegations will enflame a row that broke earlier this month when Kabul revealed it had shared intelligence with Islamabad that Taliban leader Mullah Omar was hiding in Pakistan and terrorist training camps on its soil were churning out suicide attackers. Pakistan dismissed the intelligence as outdated and strongly criticized Afghanistan for publicizing it.

Pakistani intelligence agencies helped create the Taliban militia, but Islamabad renounced its ties with the hardline regime in late 2001 just before the U.S.-led invasion of Afghanistan to oust the Taliban for hosting Al Qaeda leaders who plotted the Sept. 11, 2001 attacks.

There was no immediate claim of responsibility for the bombing. It was the latest in a stream of suicide attacks that mark a disturbing change in tactics for Taliban-led militants fighting the Afghan government and U.S.-led coalition and NATO forces.