Syrian government forces have entered the last major opposition stronghold in the Qalamoun region on the Lebanese border, signalling a major defeat for forces opposed to President Bashar al-Assad.

The Syrian army, bolstered by fighters from the Lebanese Shia militia Hezbollah, entered the town of Zabadani on Sunday, according to pro-Hezbollah Al-Manar TV and the Syrian Observatory for Human Rights (SOHR).

"Heroic army forces in cooperation with the Lebanese resistance took control of the Al-Jamaiyat neighbourhood in western Zabadani and the Sultana neighbourhood in the east of the city," said Syrian state TV news.

"Operations are continuing with dozens of terrorists killed and wounded.”

The SOHR reported that at least 14 government and Hezbollah forces had been killed in the fighting, along with 11 opposition fighters, in the last 24 hours.

Zabadani is located 20km north of Damascus and was one of the first towns to fall to opposition hands in 2012. It has been under continuous siege by pro-Assad forces for more than a year.

Hezbollah publicly announced its participation in the Syrian Civil War in 2013, proclaiming its intention to protect Lebanon and Shia shrines within Syria from attack by “takfiri” groups likes al-Qaeda and Islamic State (IS).

Coalition pounds Raqqa

The Qalamoun advances come as the US-led anti-IS coalition pounded the IS stronghold of Raqqa in northern Syria, killing more than 30 people including six civilians, among them one child.

The fucking sutuation here in #Raqqa — Abu Ward Al-Raqqawi (@alraqqawi) July 5, 2015

"The significant air strikes tonight were executed to deny Daesh (IS) the ability to move military capabilities throughout Syria and into Iraq," spokesman Lieutenant Colonel Thomas Gilleran said in a coalition statement.

"This was one of the largest deliberate engagements we have conducted to date in Syria and it will have debilitating effects on Daesh's ability to move from Raqqa."

Photos show the destruction of Al-Sbahia bridge after hitting it by the coalition aircrafts yesterday#Raqqa #ISIS pic.twitter.com/U9OSTN5JTR — الرقة تذبح بصمت (@Raqqa_SL) July 5, 2015

Brett McGurk, deputy assistant secretary for Near Eastern Affairs, described the bombings as the "most sustained set of airstrikes to date against ISIL terrorists in Syria".

"Sixteen precision airstrikes in Raqqa will further restrict ISIL's ability to operate from its self-proclaimed capital."

The US, along with a coalition of Arab countries, began bombing IS in Syria in September 2014, with the intent to "degrade and ultimately destroy" the group, which also controls vasts swathes of territory in Iraq.

Fighting in Syria has claimed over 230,000 lives since the beginning of anti-government demonstrations in 2011.