Yesterday's killings of Nato personnel reflect a spike in tensions between Afghan and international forces that follow an American soldier's alleged massacre of Afghan civilians, the burning of Muslim holy books at a US base, and uncertainty about Afghanistan's fate as foreign troops prepare to pull out.
They also come at a time when international troops have stepped up training and mentoring of Afghan soldiers, police and government workers so that Afghans can take the lead and the foreign forces can go home.
The success of that partnership is key to the US-led coalition's strategy to withdraw most foreign combat forces by the end of 2014.
US Marine General John Allen, the top commander of US and Nato forces in Afghanistan, told reporters at the Pentagon that these types of attacks are characteristic of any warfare involving insurgents.
“We experienced these in Iraq. We experienced them in Vietnam,” Gen Allen said. “On any occasion where you're dealing with an insurgency and where you're also growing an indigenous force ... the enemy's going to do all that they can to disrupt the counter-insurgency operations.”
Since 2007, about 80 Nato service members have been killed by Afghan security forces, based on Pentagon figures released in February. More than 75% of the attacks have occurred in the past two years.
Sixteen Nato service members - 18% of the 84 foreign troops killed so far this year - have been shot and killed by Afghan soldiers and policemen or militants disguised in their uniforms, according to the tally.
On Monday, two British service members were killed by an Afghan soldier in front of the main gate of a joint civilian-military base in southern Afghanistan, the coalition said.
Another coalition service member was shot and killed at a checkpoint in Paktika province in eastern Afghanistan by a man who was believed to be a member of a village-level fighting force the US is fostering in hopes of countering the Taliban insurgency, local officials said. A US official confirmed that the service member killed was an American.
Taliban spokesman Qari Yousef Ahmadi said the shooter of the UK troops was an Afghan soldier who was in close contact with insurgents and had notified the Taliban of his planned attack before carrying it out.
However, Wahid Muzhda, a former Taliban foreign ministry official and an analyst on issues related to the group, said the Taliban were not behind most of the latest killings.
“All these killings are not linked to the Taliban,” Mr Muzhda said. “The recent Koran burnings and the shooting spree - the killing of children - are affecting the minds of the Afghan soldiers. They think the foreigners are looking out for their own interests. They think if the foreigners are coming here to defend Afghanistan, why are they killing children?”
The trust between the Afghan forces and their international mentors is being undermined, he said.