JOIN USThe Taliban, the main militant group leading an escalating 10-year insurgency, claimed responsibility for the attack in Gardez, the capital of eastern Paktia province, which borders Pakistan.
"The bomber was in a vehicle. He tried to enter the base (but) the guards did not let him. He was frustrated and detonated at the very, very first gate," a coalition spokesman said."Two Afghan-contracted guards were killed," he said.
Earlier the Paktia provincial police chief told AFP three people, two contracted guards and a border police officer in a nearby police base had been wounded.
"A suicide bomber tried to attack the base with a truck bomb but he was encountered at the first gate by Afghan guards. He set off his bombs there," Paktia provincial police chief, Abdul Ghafar Sapai, told AFP.
He said the distance between the first barrier and the main gate was more than 100 metres.
The police chief said "good security measures", including anti-blast concrete blocks, stopped the attacker from reaching his target and causing more casualties.
The base houses small groups of troops and civilian experts who are trying to help rebuild the war-torn country and enhance security. The groups are known as Provincial Reconstruction Teams (PRT) and are assigned across Afghanistan.
The PRTs are run by various Western nations as part of NATO's US-led International Security Assistance Force mission in Afghanistan. The Gardez PRT is run by the United States.
ISAF headquarters in Kabul could not give immediate information.Taliban spokesman Zabihullah Mujahed, contacting AFP from an undisclosed location by telephone, said one of their fighters drove a bomb-laden car into the entrance of the base and detonated his explosives.
Mujahed said that dozens of US and Afghan troops were killed and wounded.