GENEVA, Sept 28 (Reuters) - The United Nations human rights council on Friday extended the mandate of its investigation into war crimes in Syria by another six months.

It also condemned widespread violations by Syrian government forces in the 18-month-old conflict.

The 47-member Geneva forum adopted a resolution submitted by Arab states by a vote of 41 states in favour, with three states - China, Cuba and Russia - against and three abstentions.

Syria's ambassador Faysal Khabbaz Hamoui rejected the text as "highly-politicised and selective" and accused Islamic "terrorists" of fueling the violence in his country.

Since it was set up a year ago, the independent inquiry led by Brazilian Paulo Pinheiro has interviewed more than 1,100 victims, refugees and defectors but has been denied access to Syria.

"The work of the commission of inquiry is important because as they continue to document the names of individuals responsible for these crimes and violations, they help ensure that this will not be a case where impunity prevails, but rather that those responsible for crimes against the Syrian people will face justice and accountability," U.S. ambassador Eileen Chamberlain Donahoe told the talks.

Switzerland has proposed that Carla del Ponte, a former chief prosecutor of the International Criminal Court, join the inquiry as a commissioner and an announcement was expected by the end of the day, diplomats said.

Also on HuffPost:

Loading Slideshow...
  • Laura Dupuy Lasserre of Uruguay, President of the Human Rights Council, briefs the media on the conclusion of the 21th regular session of the U.N. Human Rights Council, at the European headquarters of the United Nations in Geneva, Switzerland, Friday, Sept 28, 2012. (AP Photo/Keystone, Martial Trezzini)

  • Eileen Chamberlain Donahoe, U.S. Representative to the Human Rights Council, listens before the vote after the Syria draft resolution was just adopted by the Council during the 21th session of the Human Rights Council at the European headquarters of the United Nations in Geneva, Switzerland, Friday, Sept. 28, 2012. (AP Photo/Keystone, Martial Trezzini)

  • Faysal Khabbaz Hamoui, Syrian Ambassador in Geneva, listens before the vote after the Syria draft resolution was just adopted by the Council during the 21th session of the Human Rights Council at the European headquarters of the United Nations in Geneva, Switzerland, Friday, Sept. 28, 2012. (AP Photo/Keystone, Martial Trezzini)

  • A screen shows the results of the vote after The Syria draft resolution was just adopted by the Council during the 21th session of the Human Rights Council at the European headquarters of the United Nations in Geneva, Switzerland, Friday, Sept. 28, 2012. (AP Photo/Keystone, Martial Trezzini)

  • In this image taken from video obtained from Shaam News Network (SNN), which has been authenticated based on its contents and other AP reporting, a body is taken from the rubble of a building destroyed by a government airstrike in Azaz, Syria, Friday, Sept. 28, 2012. (AP Photo/Shaam News Network SNN via AP video)

  • In this image taken from video obtained from Shaam News Network (SNN), which has been authenticated based on its contents and other AP reporting, Syrians dig through rubble of a building destroyed by a government airstrike as they search for survivors in Azaz, Syria, Friday, Sept. 28, 2012. (AP Photo/Shaam News Network SNN via AP video)

  • In this image taken from video obtained from Shaam News Network (SNN), which has been authenticated based on its contents and other AP reporting, a body is taken from the rubble of a building destroyed by a government airstrike in Azaz, Syria, Friday, Sept. 28, 2012. (AP Photo/Shaam News Network SNN via AP video)

  • In this image taken from video obtained from Ugarit News, which has been authenticated based on its contents and other AP reporting, Syrian rebels are seen during an operation in Aleppo, Syria, Friday, Sept. 28, 2012. (AP Photo/Ugarit News via AP video)