An Afghan policeman opened fire with a heavy machine gun on a security meeting between US special forces and Afghan soldiers and police, killing two Americans and five Afghans, and injuring more than a dozen others in one of the deadliest “insider attacks” for months.
A few hours later, two Afghan truck drivers were shot dead by US forces when they were driving near a military convoy on the outskirts of Kabul. A third man was injured.
Nato forces confirmed the deaths, saying the soldiers acted in self-defence after the men "failed to heed instructions to stop".
A senior Afghan police officer said the shooting began after the men had parked their truck. The civilian deaths in Kabul and the attack in Wardak province, a short drive west of the capital, underlined major frustrations of both Afghans and Americans, and is likely to inflame tensions between the two uneasy allies.
They came hours after new US defence secretary Chuck Hagel wrapped up a fractious first visit to Afghanistan during which Afghan president Hamid Karzai accused the US of colluding with the Taliban. The incidents also came a day after a deadline laid down by Karzai for American special forces to leave Wardak province, following allegations of abuse.
The US ambassador in Kabul, James Cunningham, said it was "inconceivable" that the US would work with the Taliban, after spending billions and losing over two thousand soldiers in Afghanistan.
“The thought that we would collude with the Taliban flies in the face of everything we have done here and is absolutely without foundation,” he said in a statement.
Nato confirmed that two soldiers had been killed, and several wounded in Wardak, but declined to comment on the number or severity of the injuries, or the details of the shooting.
The Wardak shooting came just three days after another insider attack in eastern Afghanistan, when three men from the Afghan army shot dead a US soldier.
There has been a steady stream of Afghan soldiers and police turning their guns on Nato soldiers who are meant to be their allies in recent years, undermining morale and raising questions about plans for a long-term training programme in the country.
The toll from the attacks has been rising despite a string of Nato measures to protect their troops, including having armed "guardian angels" watch over all meetings with Afghan counterparts. Afghan security forces are also very vulnerable to insider attacks, and in Wardak the district police chief was badly injured along with US troops, the deputy provincial police chief Abdul Razaq said.
“Around 9am the Afghan national army commando unit, the Afghan local police, the Afghan national police and the US special forces were all inside, and planning to go on patrol, when suddenly the ALP driver climbed up to the machine gun on the ranger police truck and opened fire,” Mr Razaq said.
The attacker was killed, and the district police chief and his bodyguard were wounded, Mr Razaq added.
A young boy, standing on a rooftop around a kilometre away to watch the fighting, was also killed, said MP Abdul Ahmad Durrani, who was a Mujahideen fighter against Soviet troops and once commanded troops on the same site where US forces are now based.