Tests that were conducted on wounded Syrians who arrived in Turkey suggested that chemical weapons may have been used by Syrian security forces, the Turkish foreign minister said on Friday, according to Al Arabiya.

Ahmet Davutoglu, who spoke from Amman, said that further tests were being conducted in order to verify the recent evidence.

“We have been making tests and we have some indications regarding chemical weapons being used, but in order to make sure and verify we are continuing these tests and will be sharing these tests with UN agencies,” Davutoglu said.

U.S. Secretary of State John Kerry also said on Friday there was “strong evidence” that the regime of Syrian President Bashar al-Assad had used chemical weapons against rebel forces.

“This fight is about the terrible choices that the Assad regime has made with its willingness to kill anywhere… to use gas, which we believe there is strong evidence of use of,” Kerry said during a Google+ hangout and was quoted by AFP.

On Thursday, Turkey’s prime minister, Recep Tayyip Erdogan, also charged that Assad’s government had used chemical weapons against its people, telling NBC News that he believes President Obama’s “red line” was crossed “a long time ago”.

Britain on Thursday said it believed it was “very likely” the Syrian government used chemical arms, reported Al Arabiya. British prime minister David Cameron said there was no proven evidence Syrian opposition fighters used such weapons.

The White House notified lawmakers late last month that the United States had established, with “varying degrees of confidence,” that a sarin gas attack had taken place in Syria, leading to increased pressure on Obama to act in Syria.

The White House has said it is considering all its options, including reviewing its opposition to date to providing weapons to rebels.