Updated

The Latest on Syria developments (all times local):

2:35 p.m.

Turkish Prime Minister Binali Yildirim says the use of chemical weapon against civilians in a Damascus suburb is "unforgivable" but says Turkey is urging all sides to refrain from actions that will cause further turmoil in Syria.

Yildirim on Friday again condemned the "heinous" the attack in Douma and said the perpetrators should "pay a price."

"However ... any action that would lead to the failure or harm activities led by Turkey, Iran and Russia toward a lasting peace should be avoided," Yildirim said. He was referring to the three countries' efforts to reduce violence in Syria.

Syrian opposition activists and medics say a suspected gas attack last week killed more than 40 people in Douma. The Syrian government has denied the allegations.

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1:35 p.m.

Russia's foreign minister has asserted that a suspected chemical attack in the Syrian town of Douma last weekend was fabricated with the help of an unspecified foreign intelligence agency.

Sergey Lavrov says Russian experts have inspected the site of the alleged attack in Douma, just east of Damascus, and found no trace of chemical weapons. He says Moscow has "irrefutable information that it was another fabrication."

Lavrov spoke to reporters in Moscow on Friday.

He said that "intelligence agencies of a state that is now striving to spearhead a Russo-phobic campaign were involved in that fabrication." He didn't elaborate or name the state.

The attack has drawn international outrage and prompted the United States and its allies to consider a military strike on Syria, something Moscow has strongly warned against.