KABUL: A man in an Afghan army uniform turned his weapon on the international troops working with him in the country's east on Saturday, killing three of them, while an attacker with a grenade killed an Italian soldier in the west, officials said.

The eastern shooting was the latest in a string of so-called ''insider attacks'' in which Afghan forces open fire on their comrades or international forces.

The incidents threaten to shake the confidence and trust of the two sides as the 2014 withdrawal of most of the international troops approaches.

The international coalition in Afghanistan gave few other details of the latest attack. It does not release the nationalities of casualties until their home countries announce them.

The Taliban insurgents claim most of the insider attacks, but the international coalition has said some of them are sparked by personal disputes.

In the western province of Farah, meanwhile, an Italian soldier was killed and three others wounded when an attacker lobbed explosives into their armoured vehicle in western Afghanistan, Italy's government said.

The Defence Ministry said the attack in Farah province came as the Italian soldiers were returning to their base from training Afghan security forces.

The Italian convoy of three armoured vehicle apparently had been slowed by traffic near an intersection when an attacker ran up and threw an explosive device into the lead vehicle, the ministry said. It added that the three wounded soldiers' injuries were not life-threatening.

The Taliban quickly took responsibility for the attack with spokesman Qari Yousef Ahmadi claiming that the attacker was an 11-year-old boy.

But Farah province provincial government spokesman Abdul Rahman Zhawandai says an adult man was seen throwing a grenade, then escaping by blending into the crowd at a nearby vegetable market.

Taliban insurgents have launched intense attacks across the country as Afghan forces take over most security responsibility ahead of most foreign troops' withdrawal next year.

Saturday's deaths brought to 16 the number of international troops killed in Afghanistan this month. On Thursday, seven Georgian soldiers died in a truck bombing at their base in the south.