Islamist rebels in eastern Syria have ordered women to put on the Islamic veil, warning that anyone not doing so would be held to account, in a concerted new attempt by hardliners to impose their strict views on society, Reuters reports.

In a statement, an organization calling itself the Islamic Law Council of Deir al-Zor gave women until the end of the week to don the face veil. It did not say what punishment would befall women who fail to comply with the order.

Armed Islamist groups have become the most powerful force in the almost three-year-old uprising against President Bashar al-Assad, who has long portrayed himself as the defender of a secular order in Syria.

"Given that sins are the main reason delaying victory, the legal council in the town of Deir al-Zor is obliged to promote virtue and prevent vice," said the statement posted by an activist on Facebook and also reported by the Syrian Observatory for Human Rights, whose monitors records violence in the Syrian civil war.

Last month, the New York-based Human Rights Watch reported that the Nusra Front and the Islamic State of Iraq and the Levant - both hardline Islamist rebel groups - were enforcing their strict interpretation of Islamic law by requiring women to wear head scarves and full-length robes.

Citing interviews with refugees, Human Rights Watch also said Islamists were imposing discriminatory rules banning women and girls, particularly those not abiding by their dress code, from moving freely in public, working and going to school.