A person wearing  National Security Force uniform shot dead three foreign advisors working for the International Security Assistance Force (ISAF) in western Herat province on Sunday, said officials.

In other incidents, five NATO service members were killed in roadside bombings over the past two days.

All five of the NATO service members were killed in roadside bomb attacks - one Saturday in the east, and on Sunday, two in the east and two in the south. NATO provided no further details on the incidents or the nationalities of the troops.

NATO also said that it killed a number of Taliban with an airstrike in the Mohammad Agha district of eastern Logar province. It did not provide further details.

But Taliban announced that Mujahideen of the Islamic Emirate on Saturday targeted the invaders army base located in Muhammad Agha district of Logar province with missiles and rockets causing the enemy deadly losses.

Fighting in eastern Afghanistan, particularly in Logar province, has been raging since spring as NATO tries to clear the area of Mujahedeen.

US forces did not provide any details about the exact location of the incidents or the nationalities of the troops, as per its protocol.

The deaths bring the number of foreign troops to 250 so far this year in Afghan war, according to iCasualties.org which tracks the number foreign troops killed in Afghanistan.

Meanwhile armed men killed five security guards working for a Nato base in central Maidan Wardak province early Sunday, local officials said.

Six security guards were abducted by the rebels, reportedly Taliban, on Saturday afternoon in Mullah Khil area of Jalriz district, but one escaped, provincial spokesman Shahidullah Shahid said.

"Last night, one of the security guards escaped the area and the dead bodies of at least five Afghan private security guards were recovered in the province," he said.

The Taliban has not yet commented on the incident yet.

Wardak province shares its eastern border with Kabul province.

An IED attack in the province last fortnight killed six US soldiers travelling in a mine-resistant vehicle - the single loss of life for the US in an incident this year since the January 19 helicopter crash in Helmand province killed six US marines.

Also Sunday, Afghan officials reported that four civilians died when hundreds of shells and rockets were fired from neighboring Pakistan.

The artillery shells hit homes along frontier areas from which Taliban have in the past staged cross-border attacks.

There is little or no government or NATO military presence in the area and large swaths of the region are controlled by militants groups.

The Afghan government has not openly blamed the Pakistani military for the artillery barrage, which reportedly hit districts in the eastern provinces of Nuristan and Kunar.

Hamid Karzai discussed artillery fire coming from Pakistan at a weekly meeting of his national security council, a statement said. It added that Karzai ordered an in-depth investigation into the attacks.

The cross-border attacks were discussed in Kabul last week during an official visit by Pakistan's new Prime Minister Raja Pervaiz Ashraf and British Prime Minister David Cameron.

Cameron, Ashraf and Karzai jointly called for a common stand against insurgents operating in the lawless border areas. Ashraf complained at a news conference about attacks against Pakistan originating in Kunar.

Kabul's Foreign Ministry spokesman Janan Mosazai said, ‘The rocket attacks in the eastern provinces of Afghanistan are not acceptable to us, and we are strongly condemning these attacks. We believe that the continuation of such rocket attacks will have a negative impact on the friendly relations between Afghanistan and Pakistan.’

Also on Sunday morning at about 8:00 a.m. local shot down a US helicopter in the center of Kamdish district of Nooristan province leaving as many as 18 soldiers aboard the helicopter dead, Taliban claimed.

Taliban also says that heavy clashes erupted in Zafararyano area near Sangin district of Helmand province when Taliban initially targeted the combined enemy troops with 2 simultaneous IED blasts and then engaged them in hand to hand combat.