BEIRUT  - An offensive by the militant of Islamic State group against Syrian government-held territory has killed at least 74 people in the past 24 hours, a monitoring group said on Friday. Buoyed by their capture of swathes of western and north-central Iraq last month launched multiple attacks on army positions across northern and northeastern Syria on Thursday.

The Syrian Observatory for Human Rights said it was the first time that IS, accused by rival rebel groups of focusing its formidable firepower more on them than on the Damascus regime, had launched such coordinated assaults on army positions.

The militants went on the offensive near the main northern city of Aleppo, in Hasakeh province in the northeast and in Raqa province around their Euphrates valley stronghold, the Observatory said.

The IS, which in June announced a “caliphate” straddling Syria and Iraq, controls swathes of both countries and is seeking to seize more territory. The Britain-based Observatory said at least 74 people were killed in clashes in 24 hours, mainly in Hasakeh and Raqa. It said the toll included at least 32 militants, 30 soldiers and 12 members of the ruling Baath party of President Bashar al-Assad.

In Hasakeh’s provincial capital of the same name, four suicide bombers launched an attack inside the local Baath headquarters. Among the 12 dead was “a Baathist who was decapitated with a sharp instrument”, said the Observatory, which relies on activists and medics on the ground for its information.

South of Hasakeh city, 11 soldiers were killed in an IS attack on an army position and 17 militants were killed, it said. “Regime bombardment forced the IS to withdraw overnight,” Observatory chief Rami Abdel Rahman said on Friday.

In Raqa province, which is mainly held by IS, the militants attacked two positions of the army’s 17th Division, sparking fighting that left dozens of dead and wounded, the Observatory said.

In one attack, two suicide bombers - one a Saudi - blew up trucks packed with explosives. “At least six soldiers, one an officer, were decapitated and eight militants were killed,” the Observatory said.

IS posted photographs on its Twitter account of six decapitated corpses that it said were soldiers of the 17th Division. “The IS wants to ‘clean’ the province of any army presence,” Abdel Rahman said.

East of Aleppo, the militants attacked the Kuwayris airbase, sparking fierce fighting on Thursday that has since died down, the Observatory said. The more than three-year conflict in Syria is becoming increasingly complex as the IS battles regime forces, mainstream rebels, its former allies of Al-Qaeda affiliate Al-Nusra Front, as well as Kurdish militia.

IS militants are seeking to expand the fiefdom they have carved out along the Euphrates Valley by taking the battle to neighbouring government-held areas after routing rival rebels in Deir Ezzor province in Syria’s east earlier this year.

Meanwhile, Jordan shot down a drone on Friday as it flew over the northeastern region of Mafraq, near the border with Syria, a security official said. In the first such incident since the conflict erupted in neighbouring Syria in 2011, “the Jordanian armed forces shot down an unidentified drone with a missile as it flew over Mafraq,” the official told AFP.

“It was a violation of Jordan’s airspace. Jordan will take measures at a high level after identifying the drone.”

The official said the drone flew near the Zaatari refugee camp, which is home to around 100,000 Syrian refugees. “There were no injuries. The armed forces sealed off the area where the drone was shot down by a surface-to-air missile and have begun an investigation,” he said.