A man in an Afghan army uniform has shot and wounded coalition troops in eastern Afghanistan in the latest incident of an insider attack.

Nato said wounded were being treated but did not say how many were hurt or provide any other details about the attack in eastern Wardak province's Sayed Abad district. The coalition maintains a large base there, but Nato did not say where in the district the attack took place or what happened to the gunman.

Three British soldiers were killed on Sunday by an Afghan policeman in southern Afghanistan's Helmand district.

That attack brought the total number of "Green-on-Blue" killings, involving Afghan security officials attacking Nato allies, to 26 in 18 incidents this year. That compares with 11 fatal attacks and 20 deaths the previous year. In 2007 and 2008 there were four attacks and four deaths.

Officials do not routinely report such attacks where troops are wounded.

Efforts to draw down the number of foreign troops in Afghanistan rely on them working closely with their Afghan partners to train and mentor them so that they can take over the security of their country by the end of 2014. But such insider attacks fuel distrust and have triggered increased security protections for foreign troops serving in Afghanistan.

A total of 220 foreign troops have been killed this year, including five in July.