The Islamic State’s attack on the Syrian city of Deir Ezzor may have killed hundreds of people, human rights activists claim. Meanwhile, Syria has blamed foreign powers for the “bloody massacre.”

The UK-based Syrian Observatory for Human Rights said on Sunday that around 400 civilians, who were earlier abducted by ISIS, might have been executed. The Observatory is not the only one to make such claims.

Syria’s official news agency SANA claimed around 300 civilians, consisting mostly of children, women and elderly people, had been killed in al-Bghailiye village in Deir Ezzor’s western countryside.

The Foreign and Expatriates Ministry blamed regional and international powers, which support armed terrorists in the country, for the death of hundreds of civilians.

The ministry sent two identical letters to the UN Secretary-General and the head of the UN Security Council. In the letter, it confirmed the ISIS attack on Jan. 16.

“In this regard, we underline the destructive role played by France whose diplomacy has become proficient in firing off nonsense which encourages the committing of terrorist acts by demonizing the forces that are actually fighting terrorism,” SANA quotes the letter as blaming countries like Qatar, Turkey and Saudi Arabia.

The letter names a number of organizations as “terror organizations.” It asked the UN Security Council to take action against “ISIS, Jabhat al-Nusra, Jaish al-Islam (Islam Army), al-Jabha al-Islamiya, Jaish al-Fateh (Conquest Army), the Free Army, Ahrar al-Cham, and other organizations.” It adds that those organizations are threats to world peace.

According to the Observatory, the Syrian government is bringing in additional forces to reinforce the defence. CNN reports ISIS has killed dozens of Syrian soldiers in the last few days. The terrorist group has also captured a number of civilians.

Deir Ezzor happens to be a strategic point which is surrounded by a number of ISIS’ oil fields. The city also has roads leading to Palmyra in Homs province and Iraq.