Nine children have been killed following a rocket attack by Islamic State terrorists on a school in Deir Ezzor, an oil-rich region in the east of Syria. A further 15 school kids were injured, three of whom are in a critical condition.

“We went to work as usual at eight in the morning. The girls' group was having a physical education lesson in the yard. The first bomb fell at 8:20am,” Droubi Mohammed al-Ali, the director of the Maisalune middle school, told RT in a telephone interview.

“We tried to make sure that the students would not come to any harm, but unfortunately this was not the case, as nine girls were killed and around 15 were wounded, three of whom are in a critical condition,” he added.

The rocket attacks struck the Harabesh neighborhood of the city and hit the all-girls school. Al-Ali confirmed that the rockets had been fired from an area controlled by Islamic State (IS, formerly ISIS/ISIL). He added that those affected were in the seventh and 10th grades.

The Syrian cabinet condemned the attack, saying it would not give in to the terrorist group.

“Such crimes against schools and universities will not deter us from continuing the educational process for future generations to rebuild the country,” Prime Minister Wael Nader Al-Halqi said.

IS has often targeted residential districts in the city to try and destabilize the security and stability of the area. The jihadist organization has also looked to terrorize those sections of the local population who do not ascribe to its doctrines.

The area around the city of Deir Ezzor is of crucial importance to IS due to its oil resources. The terrorist group has been running an oil-smuggling operation from the region to help fund its war against the Syrian government of President Assad.

The Russian Defense Ministry released evidence three weeks ago which it said unmasked a vast illegal oil trade carried out by IS, adding that Turkey was the main destination for smuggled petrol. Moscow implicated the Turkish leadership in aiding the terrorists.

“According to our data, the top political leadership of the country – [Turkish] President Erdogan and his family – is involved in this criminal business.”

However, since the start of Russia’s anti-terrorist operation in Syria on September 30, the income of IS militants from illegal oil smuggling has been significantly reduced, the ministry said.

“The income of this terrorist organization was about $3 million per day. After two months of Russian airstrikes their income was about $1.5 million a day,” Lieutenant-General Sergey Rudskoy said at the beginning of December.