Moscow insisted on Tuesday that a new Security Council resolution on Syria not allow the use of force, while the Arab country’s main opposition group demanded a swift international response following the U.N. report that confirmed chemical weapons were used outside Damascus last month.

Meanwhile, a car bomb exploded at a crossing point along Syria’s volatile border with Turkey, Syrian activist groups said. At least 15 people were wounded in the explosion at the rebel-controlled Bab al-Hawa crossing, they said.

The explosion at the border crossing with Turkey on Tuesday was not the first such attack. In February, a car bomb exploded at the border post, killing 14 people and narrowly missing 13 Syrian opposition figures who were crossing into Turkey. And in May, 43 people were killed when two car bombs exploded on Turkish side of the border.

In Moscow, Foreign Minister Sergey Lavrov said Russia “spoke clearly” about rejecting the use of force when the agreement on Syria abandoning its chemical weapons was worked out in Geneva between U.S. and Russian envoys.

But if signs emerge that Syria is not fulfilling the agreement or there are reports of further chemical weapons use, “then the Security Council will examine the situation,” Lavrov said, suggesting the issue could be reconsidered. He spoke at a news conference with French counterpart Laurent Fabius. France and the United States say a military option remains on the table and are pushing for the U.N. resolution to reflect that.

The meeting in Moscow came a day after U.N. inspectors submitted their report on the Aug. 21 chemical weapons attack that precipitated the heightened tensions over Syria. It was the first official confirmation by impartial experts that chemical weapons were used in the attack near Damascus, which killed hundreds.

Although the report confirmed chemical weapons were used, it did not say who used them — and Lavrov and Fabius differed sharply on their interpretations.

“The report exposes the regime,” Fabius said. “On the basis of the information of our external agents, we consider that the report proves the responsibility of the regime for the chemical weapons attack of Aug. 21.”

The U.S., Britain and France jumped on evidence in the report — especially the type of rockets, the composition of the sarin agent, and trajectory of the missiles — to declare that President Bashar Assad’s government was responsible. Russia, a staunch ally of the Syrian regime, disagreed.

Lavrov said the Russian side has “serious reason to suggest that this was a provocation” by the rebels fighting Assad’s forces.

In Damascus, the Foreign Ministry slammed the U.S., British and French foreign ministers, accusing them of trying to impose their agenda on the Syrian people. The ministry statement came in response to recent demands by the three ministers that Assad step down even as the West increases efforts to bring the warring sides to an international peace conference.

The statement denounced the three ministers for “their frantic quest to impose their will” on the Syrian people, stressing that any talk about the political and constitutional legitimacy in Syria is an “exclusive right for the Syrian people.”

“It’s impermissible for the United States, its allies and tools” to impose their will in this regard, the statement said. “Assad is the legitimate president chosen by the Syrian people and will remain so as long as the Syrian people want this.”

The main Syrian opposition group, the Western-backed Syrian National Coalition, said the U.N. report offered “damning and irrefutable evidence” and clearly shows that only the Syrian regime could have carried out the attack, which U.N. chief Ban Ki-moon denounced as a “war crime.”

The U.N. inspectors report said surface-to-surface rockets loaded with the nerve agent sarin had been fired from an area where Syria’s military has bases, but said the evidence could have been manipulated in the rebel-controlled neighborhood that was struck.