The Islamic State group, also known as ISIS, hung bodies of four Syrian rebels in the far northeastern governorate of Al-Hasakah, the Syrian Observatory for Human Rights said Wednesday.

ISIS hung the bodies of the Syrian Democratic Forces fighters in Al-Hasakah’s village of Janah after they were killed in clashes against the Sunni militant group Tuesday, the U.K-based monitoring group said. No further information on the fighters or the incident was immediately available.

The incident comes as Russia started pulling out its troops from Syria. On Tuesday, the Russian Defense Ministry said that the first group of Russian warplanes left the Hemeimeem air base in Syrian coastal province of Latakia. The United Nations hailed the move as a “positive step” for a fresh round of talks backed by the U.N. to potentially end the five-year Syrian conflict.

Russian President Vladimir Putin on Monday announced the decision to pull out most of the country's troops from Syria in a televised meeting with his defense and foreign ministers. He said that Moscow's five-month air campaign has helped Syrian President Bashar Assad to “radically” turn the tide of war and helped create favorable conditions for the much awaited peace talks.

The talks aim to resolve the long-running conflict that has reportedly killed 250,000 people and displaced over 5 million others.