UN Secretary-General Antonio Guterres voiced alarm on Wednesday (March 21st) over allegations of chemical attacks in Syria and urged the Security Council to take action to address "such serious crimes", AFP reported.

The appeal came after Guterres met on Tuesday with the head of the Organisation for the Prohibition of Chemical Weapons (OPCW), which has investigated more than 70 cases of toxic gas attacks in Syria since 2014.

"The secretary-general is alarmed at the persistent allegations of the use of chemical weapons in the Syrian Arab Republic," said a UN statement.

While the use of chemical weapons is "unjustifiable and abhorrent, equally unjustifiable is a lack of response to such use", said the statement.

"Impunity cannot prevail with respect to such serious crimes."

Guterres renewed a call to the council "to demonstrate unity and resolve on this matter".

OPCW chief Ahmet Uzumcu said there had been "several" recent allegations of chemical weapons use in Eastern Ghouta, where the Syrian government is battling to take control over the enclave near Damascus.

The Syrian Observatory of Human Rights has said that chlorine has been used as a toxic agent on villages during the government's offensive in Eastern Ghouta.

Uzumcu said the experts were looking into allegations of chlorine use that were attributed to the Syrian army and to opposition groups.