More than 130 terrorists from the Islamic State (ISIS) have been killed in a US-backed offensive on the key jihadist-held city of Manbij in northern Syria, a monitoring group said Thursday.
US-led coalition air strikes supporting the assault by Kurdish and Arab fighters, launched on May 31, have also left 30 civilians dead, said the Syrian Observatory for Human Rights.
The Syrian Democratic Forces have been pushing west from the Euphrates River and have nearly encircled Manbij, a key point along ISIS's main supply line from the Turkish border to its eastern Syrian stronghold of Raqa.
The SDF alliance has surrounded the city from the north, east and south. Early on Thursday its fighters were advancing towards the main road leading west out of Manbij, according to Observatory head Rami Abdel Rahman.
A statement on Thursday by the SDF's Manbij operations center said its fighters were now close enough to target ISIS positions inside the city.
The Britain-based Observatory, which relies on a network of activists and medical sources inside Syria, said 132 ISIS jihadists and 21 SDF fighters had been killed since the start of the offensive.
"Most of the Daesh fighters were killed in air raids by the international (US-led) coalition," Abdel Rahman told AFP, using an Arabic acronym for the group.
He said dozens of bodies of ISIS fighters had been found on Thursday morning in small villages east of Manbij.
Coalition air raids supporting the assault also killed at least 30 civilians, including 11 children, the Observatory said.
They are among a total of 447 civilians killed in coalition raids since they began in Syria in September 2014, according to the monitor's tally.
The Observatory says it determines whether strikes are carried out by Syrian, Russian or US-led coalition aircraft based on their locations, flight patterns and the types of planes and munitions involved.
A spokesman for the US defense department said on Wednesday that the final assault on Manbij could take place within days.
AFP contributed this report.