NATO-led forces in Afghanistan say three international troops have been killed in two separate incidents by men wearing local police or army uniforms.
The attacks appeared to be the latest in a series of so-called "green on blue" attacks, in which Afghan security forces have targeted their international colleagues or mentors.
In the first incident on March 26, a man wearing an Afghan Army uniform shot and killed two British soldiers inside a NATO base in southern Afghanistan.
International Security Assistance Force (ISAF) spokesman Major Jason Waggoner said NATO forces returned fire, killing the gunman, after he turned his weapon on NATO soldiers.
Officials said that attack occurred at a base in Lashkar Gah, in Helmand Province.
It was not immediately clear what prompted the shooting.
In the second incident, an international soldier was shot dead by an "alleged member" of the Afghan police force in the east of the country. ISAF officials declined to identify the victim's nationality.
Such attacks have become increasingly common over the past year, particularly since the accidental burning of Korans at a U.S. base in February, and the alleged massacre of 17 Afghan civilians by a U.S. soldier earlier this month.
The commander of U.S. and NATO forces in Afghanistan, General John Allen, told a U.S. Senate committee last week that 13 members of the NATO-led force had been killed this year in what appeared to be attacks by members of Afghan forces, their supposed allies.
The U.S. Defense Department has reported that there have been more than 45 attacks by Afghans on their NATO colleagues since 2007 -- more than 75 percent of those in the last two years.
Staff Sergeant Robert Bales is being held at a U.S. military prison at Fort Leavenworth, Kansas, in connection with the massacre of the 17 villagers.
He is accused of leaving his base in Kandahar Province in southern Afghanistan on March 11 and killing eight Afghan adults and nine children.
The United States has been facing increased pressure in Afghanistan following the massacre and the Koran incident.
The Taliban has vowed "strong revenge" for the Kandahar shootings, and also announced that it had suspended preliminary talks in Qatar with the United States aimed at building confidence for full-scale peace negotiations.
Following the Kandahar killings, Afghan President Hamid Karzai called for NATO troops to leave Afghan villages and to remain only on major bases.
Karzai has also told Washington that he wanted Afghan forces to take control of Afghan security from NATO forces in 2013 -- not in 2014, as planned by Washington, when foreign forces are now scheduled to leave Afghanistan.
Talks In Dushanbe
At a conference in the Tajik capital, Dushanbe, on March 26, Iranian President Mahmud Ahmadinejad slammed U.S. policy in Afghanistan as the source of all of Afghanistan's problems.
Ahmadinejad's remarks prompted the U.S. delegation to walk out of the conference.
Ahmadinejad said the United States went into Afghanistan in late 2001 under the pretext of fighting terrorism, and was now using the same pretext to encircle the whole region.
Leaders from Afghanistan's neighboring states, as well as a U.S. delegation led by Assistant Secretary of State Robert Blake, attended the Dushanbe conference.
U.S.-led forces invaded Afghanistan and toppled the Taliban regime in the aftermath of the September 11, 2001, terrorist attacks in the United States that were carried out by the Al-Qaeda network, allies of the Taliban.
U.S. forces have remained in the country to help strengthen the government of President Karzai and prevent the Taliban from returning to power.
With AP, AFP, and Reuters reporting