DAMASCUS, July 26 (Xinhua) -- As many as 85 government soldiers have been killed over the past two days as a result of attacks launched by the so-called Islamic State (IS) on a military base in Syria's northern al-Raqqa province, activists said Saturday.

The 85 soldiers and officers have been confirmed dead during the twin bombings the IS had staged at the gates of the 23rd Division base in al-Raqqa and the clashes that ensued, said the UK- based Syrian Observatory for Human Rights.

The Observatory said that the IS, which is an al-Qaida splinter group, had also executed soldiers who were retreating toward northern al-Raqqa after fleeing the base.

The IS has also published haunting images of beheaded soldiers it had slain in al-Raqqa, while the Observatory added that the destiny of other 200 soldiers is still unknown.

The IS at dawn Thursday unleashed large-scale offensives on the 23rd Division of the Syrian army in al-Raqqa, which has fallen to the group since last year except for the division and another airport in the area called al-Tabakka military airbase.

The IS, previously known as the Islamic State in Iraq and the Levant (ISIL), has recently proclaimed the establishment of an " Islamic Caliphate" straddling Syria and Iraq, and changed its name into the "Islamic State."

The group led by Abu Bakr al-Baghdadi, who commands tens of thousands of fighters, said their goal is to establish an Islamic state in Iraq and Syria to fight the Shiite government of Iraqi Prime Minister Nouri al-Maliki and that of Syrian President Bashar al-Assad, whose top ranks are from the Alawite minority, an offshoot of Shiite Islam.

Syria has been gripped by deadly conflict since March 2011. Over 160,000 people have reportedly been killed and millions displaced due to the violence.