The NATO commander in Afghanistan has ordered tougher security measures to protect allied soldiers from being shot by Afghan forces, officials said Thursday, amid growing anxiety about a rise in "insider" attacks.

US General John Allen's orders issued in recent weeks call for advisers to carry weapons when appropriate and for NATO units to always designate one team member as a "guardian angel," who remains armed and on the look out for possible fratricidal attacks, said defense officials.

For coalition troops working at Afghan government or military buildings, the orders call for moving their desks to make sure their backs are not turned to the door, officials said, speaking on condition of anonymity.

"These (orders) have been in place a while. These were prudent force protection measures taken at the appropriate time in an appropriate way to protect our troops," Pentagon spokesman Captain John Kirby told AFP.

Allen issued the orders after close consultation with his Afghan counterparts, who fully support the measures, Kirby said.

The security precautions are a natural response to a rise in insider attacks but the steps should not be seen as having a chilling effect on NATO's cooperation with Afghan army and police, he said.

"It doesn't mean the partnership has suffered," Kirby added, saying the NATO-led force was more committed than ever to close cooperation with Afghan troops despite the surge in "green-on-blue" assaults.

"We can't let the partnership itself be a casualty of war."

Commanders view working and living in close quarters with Afghan forces as a vital part of NATO's strategy, which calls for handing over security to the Afghans by the end of 2014.

After two US advisers were gunned down last month inside the Afghan interior ministry, Allen ordered the withdrawal of all NATO advisers from government ministries until security measures could be reviewed.

Most of the advisers have yet to return to the ministry buildings but are carrying on their work by email and phone, Kirby said.

A total of 17 allied troops have been killed by Afghan forces so far this year.