Norway said Thursday that up to 5,000 NATO troops would take part in anti-submarine warfare exercises off its coast in early May, amid growing regional unease over suspected submarine sightings.

More than 10 ships and submarines as well as aircraft and helicopters would participate in the exercise between May 4 and 13 in the North Sea and in Skagerrak, the strait between Norway and Denmark.

NATO officials have voiced doubt over claims that the Islamic State group was behind a fatal bombing last week billed as the first major attack by the jihadists in Afghanistan.

The bombing on Saturday ripped through a crowd of government officials waiting to draw their salaries outside the Kabul Bank in the eastern city of Jalalabad, killing at least 34 people and wounding more than 100.

Estonia's President Toomas Hendrik Ilves has called for NATO to send more troops to his country to counter the threat posed by increasingly assertive neighbor Russia, a report said on Sunday.

Ilves told Britain's Daily Telegraph newspaper that Estonia was "part of a group of countries who are mentioned in a threatening way" by Russia and that the military alliance, which Estonia joined 11 years ago, should set up permanent combat units in his country.

An American soldier was killed Wednesday in a firefight between U.S. and Afghan troops in eastern Afghanistan, the first apparent insider attack since Washington announced a delay in troop withdrawals from the country.  

So-called "green-on-blue" attacks -- when Afghan soldiers or police turn their guns on international troops -- have been a major problem during NATO's long years fighting alongside Afghan forces.

NATO's Secretary General Jens Stoltenberg on Wednesday praised U.S. President Barack Obama's decision to keep the current level of 9,800 U.S. troops in Afghanistan until the end of 2015.

On Tuesday, Obama reversed plans to withdraw around 5,000 U.S. troops from Afghanistan this year after talks with the country's new, reform-minded leader, President Ashraf Ghani.

A Moscow-friendly Greece could paralyze NATO's ability to react to Russian aggression, former U.S. national security adviser Zbigniew Brzezinski warned Wednesday.

Athens could use its veto to slow the alliance's response if Russia set its sights on its Baltic member states, he told Poland's Dziennik Gazeta Prawna.

NATO jets were scrambled Tuesday to escort Russian fighters and nuclear-capable bombers flying near the Baltic states and Sweden with their transponders switched off, sparking protests over the danger they posed to civil aviation.

Lithuania's defense ministry spokeswoman Asta Galdikaite said NATO air policing aircraft identified two Tu-22 type bombers and two SU-27 jets. The Swedish military also confirmed the aircraft showed up on their ground radar.

U.N. Security Council member Spain called Thursday for a deal to end unrest in Libya within weeks and said a U.N. resolution would be needed to approve any NATO intervention there.

Concerned by violence and the rise of Islamist groups in Libya, Spanish Foreign Minister Jose Manuel Garcia-Margallo appeared in Madrid alongside NATO Secretary General Jens Stoltenberg to tout security cooperation in the region.

U.S. President Barack Obama saluted Sunday the "milestone" end of NATO's combat mission in Afghanistan, but warned the country remains "a dangerous place."

A low-key ceremony in Kabul marked the formal end of NATO's war after 13 years of conflict that have left the country in the grip of worsening insurgent violence. 

The Kremlin on Friday branded the expansion of NATO as a fundamental threat to Russia in a revised military doctrine that dramatically reflects deteriorating relations with the West.

The new document, approved by Russian President Vladimir Putin, decries the "reinforcement of NATO's offensive capacities directly on Russia's borders, and measures taken to deploy a global anti-missile defense system" in Central Europe.