Damascus, March 6 : The US forces have started deploying new defence systems in its bases in northern and eastern Syria to protect against any possible attack by Iran-backed militias, a war monitor reported. In a statement issued on Friday, the UK-based Syrian Observatory for Human Rights said that anti-drone air defence systems and surface-to-surface missiles were being deployed in the al-Omar oil field located in Deir al-Zour province, Xinhua news agency reported. The US forces are bringing the new equipment from its bases in Kurdish areas in Iraq, the watchdog added. More defence systems will be deployed in the coming days in all US bases in northern and eastern Syria, the statement noted. This development comes days after the US launched an airstrike on positions of Iran-backed militias in eastern Syria that killed more than 20 fighters. The airstrike was in retaliation over the attacks allegedly carried out by Iran-backed fighters against US positions in Iraq's Erbil. The Syrian government has repeatedly urged the UN Security Council to try and push the US forces out of the war-torn country, saying their presence is illegal. /IANS