At least nine schoolgirls died when IS fighters fired rockets at a school in Deir al-Zour, the Syrian Observatory for Human Rights and the state news agency SANA reported on Tuesday.

A further 20 students were wounded, according to the Syrian activists.

"The toll is likely to worsen as some of the injured are in serious condition," the Observatory's Rami Abdel Rahman told the AFP news agency.

'IS' closing in on the city

Regime forces control parts of the eastern city of Deir al-Zour and the nearby military airport, the only areas under their control in eastern Syria.

The rest of the oil-rich Deir al-Zour province is occupied by IS jihadists. IS has repeatedly attempted to drive government forces out of the city in recent months.

"The terrorist rockets will not prevent us from continuing our mission of education," Syrian Prime Minister Wael al-Halqi said.

The Syrian war has claimed the lives of over 10,000 children since 2011, according to the UN children's agency UNICEF. Millions of children are out of school.

Civil war gone global

Dozens of rebel groups, including IS and al Qaeda-affiliated Nusra front, are fighting regime forces on the ground. Kurdish and Hezbollah militants are also involved in the land war.

Iran is providing military support to Damascus, with foreign governments accusing Tehran of also deploying ground troops on Syrian soil.

In addition to the fighting on the ground, several countries are bombing the IS targets in Syria, including the US and its Arab allies, France and the UK.

The German army is also assisting the air campaign. Berlin deployed its refueling planes last week, with reconnaissance jets set to start their mission in January.

Turkey also launched a campaign targeting both the Kurdish forces and IS in August, while Russia started flying sorties against IS and other rebel groups in late September.

Over the weekend, the Lebanese Hezbollah militia accused Israel of conducting an airstrike in Syria and killing one of its members.

dj/jm (dpa, AFP)