Turkey on Sunday strongly condemned what it said was a chemical weapons attack in the Syrian city of Douma, saying there was a "strong suspicion" the regime of President Bashar al-Assad was responsible.
"We strongly condemn the attack and we have the strong suspicion it was carried out by the regime, whose record on the use of chemical weapons is known by the international community," the Turkish foreign ministry said in a statement.
Rescue workers said dozens of civilians had been killed in a chlorine gas attack on Douma -- claims denied by Assad's regime and its ally Russia.
Turkey said that the incident showed that past UN Security Council resolutions on the use of chemical weapons in Syria were "once again" being ignored.
The foreign ministry called for an investigation by the Organisation for the Prohibition of Chemical Weapons (OPCW) and said it expected condemnation from the international community.
However in recent months, Ankara has been working tightly with the Syrian regime's closest allies Russia and Iran in a bid to bring an end to the seven-year civil war.
Last week, President Recep Tayyip Erdogan hosted a summit on Syria in Ankara with President Hassan Rouhani of Iran and Russian President Vladimir Putin.
The foreign ministry statement did not explicitly refer to Russia and Iran, maintaining Turkey's caution in not lashing out at its partners.
But it called on "the parties who have influence over the Syrian regime" to ensure that such attacks are halted and punished.
It noted that "in the past no measures have been taken against these attacks".