The protests in Afghanistan against the Quran burning by U.S. troops entered its fifth day, with a UN office targeted in the north and two more NATO men killed in Kabul on Saturday.

A total of 31 people were killed and more than 180 wounded in the week-long protests. It's believed to be the most widespread one in over a decade.

Some protesters in the capital?put up?a demonstration outside the Interior Ministry and gunshots were heard shortly Saturday afternoon. The NATO-led International Security Assistance Force (ISAF) confirmed that two of its service members were killed.

"Initial reports indicate an individual turned his weapon against International Security Assistance Force service members in Kabul City today, killing two service members," said the short statement without identifying the nationalities of the victims.

Afghan Interior Ministry also confirmed the incident by saying, "Two international colleagues of Interior Ministry were killed in the premise of the ministry today afternoon." Meanwhile, a source with the ministry on the condition of anonymity said that an Afghan police opened fire and killed two U.S. advisors.

In a quick react, the ISAF decided to relocate all its forces from all the Afghan ministries following the shooting incident. The Taliban outfit in its website claimed that their officer shot dead four U.S. advisors amid protests in Kabul.

Earlier on Saturday morning, hundreds of angry mobs came to streets in the eastern Laghman's provincial capital Mehterlam and northern Kunduz city, attempting to attack government institutions and a UNAMA office. However, the anti-riot police in both cities tried hard to control the situation during which gun shots and fighting flared up.

"Four people were killed and 52 others sustained injuries and taken to hospitals," said Saad Mukhtar, the head of Kunduz Provincial Health Department. The victims included protestors and policemen, he said.

"Eleven policemen were injured in today's demonstration in Kunduz," police spokesman Syed Sarwar Hussaini told Xinhua, adding that the police have foiled protestors' attempt to attack the office of the United Nations Assistance Mission in Afghanistan ( UNAMA) in Kunduz.

In Mehterlam, people attempted to storm the governor office but police by firing succeeded to disperse them. "20 injured men have been taken to hospital in Mehterlam city," said Attaullah Niazi, director of public health in Laghman. He said two were in critical condition.

The protest demonstrations erupted Tuesday after copies of Muslim holy book Quran were allegedly burned by U.S. military in Bagram airbase, 50 km north of Kabul. With hundreds of suspected Taliban and al-Qaida operatives being held in a detention center, Bagram is the main U.S. military base in Afghanistan.

The ongoing demonstrations against the alleged Quran burning is the ever biggest and longest protest against the U.S. forces since their deployment in Afghanistan late 2001.

Afghan President Hamid Karzai has urged the people to exercise restrain besides demanding the transfer of Bagram prison to the Afghan government to avoid repeating such incidents.

However, the indignant Afghans seemed to continue their rallies, in spite of calls by officials and social figures to remain peaceful. Driven by a strong anti-American sentiment, analysts said some irrational protesters might also have taken the chance to show their dissatisfaction with the Afghan government.