A homicide bomber with explosives strapped to his chest blew himself up in a crowd of laborers outside a U.S. military base in eastern Afghanistan on Tuesday, killing as many as 10 people in the deadliest suicide attack in four months.

Renegade warlord Gulbuddin Hekmatyar, meanwhile, warned that America faces a Soviet-style humiliation and should withdraw its forces from the country, while Pakistan lodged complaints with the U.S. over the death of a Pakistani soldier near the Afghan border.

The suicide bomber struck as hundreds of Afghan workers lined up to enter the base, known as Camp Salerno, outside the city of Khost, said provincial Gov. Jamal Arsalah.

Arsalah, who visited the scene shortly after the explosion, said 10 men were killed and 14 injured. However, the NATO-led force, which includes the U.S. base, said eight Afghans, including two policemen, were killed and five wounded. It was not clear why the tallies differed. No U.S. or NATO troops were injured in the blast.

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The NATO-led International Security Assistance Force said the attacker detonated an explosives-filled vest when he reached the point where people entering the base are searched. Arsalah said concrete barriers that protect the base helped prevent a heavier toll.

Suicide attacks have become much more frequent as Taliban militants have intensified their insurgency against the Afghan government and foreign troops backing them. According to U.S. military figures, there were 139 suicide attacks during 2006, up from 27 in 2005.

Tuesday's was the deadliest since Sept. 30, when an attacker killed 12 people outside the gates of the Interior Ministry in Kabul.

Khost is a former Al Qaeda stronghold on the mountainous Pakistani border. Afghan and Western officials say insurgents use the tribal areas of neighboring Pakistan as sanctuaries from where they organize and launch operations in Afghanistan.

However, Pakistan argues that only remnants of the Taliban and Al Qaeda remain on its side of the border and complains that it gets too little recognition for deploying thousands of troops in the border region.

Underscoring the unease, Pakistan's Foreign Ministry said it summoned the U.S. and British ambassadors to protest the killing of a Pakistani soldier and wounding of two others by coalition forces near the Afghan border on Tuesday.

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The U.S. Embassy in Islamabad said Ambassador Ryan Crocker met with a senior ministry official to discuss the incident, which followed a militant rocket attack on a coalition base across the border in Bermel, eastern Afghanistan.

"The ambassador expressed deep regret for the loss of life of a Pakistani soldier and the wounding of two others and extended his condolences to the families," an embassy statement said.

NATO also expressed regret over the death and injuries, "although the cause of these casualties, and who is responsible, is as yet unclear."

A NATO statement said an airstrike had targeted insurgents moving east toward the Pakistan border, killing one and injuring another. It added that Pakistani authorities had reported its casualties "during events associated with this incident."

Meanwhile, Hekmatyar, an Afghan warlord whose fighters operate in eastern Afghanistan's mountains alongside Taliban and Al Qaeda remnants, said the U.S. faces a Soviet-style humiliation in the country and taunted Pakistan for aiding U.S.-led counterterrorism operations.

In a recording obtained by The Associated Press in Pakistan, Hekmatyar also accused Washington of fomenting conflict among Afghan ethnic groups on a scale comparable with the strife in Iraq.

"Everyone knows that the American aggressors are faced with defeat in every part of the country," Hekmatyar said. "They were unable to achieve their goals by bombing innocent Afghans, their villages and homes. They are preparing to leave like the Soviet troops."

The 24-minute recording, the third from Hekmatyar to surface this month, was undated. It was also unclear where it was recorded.