Russia said Wednesday it would press ahead with its bombing campaign in Syria until terrorist ­organizations such as the Islamic State (IS) group are defeated amid the latest international push to end the conflict.

"Russian airstrikes will not cease until we truly defeat the terrorist organizations ISIL and ­Jabhat al-Nusra," Russian Foreign Minister Sergei ­Lavrov told reporters in Oman, referring to the IS and Al Nusra Front jihadist groups, the Interfax news agency reported. "And I don't see why these airstrikes should stop," he added.

Lavrov also named "shutting down smuggling across the Turkish-Syrian ­border" as a condition for halting Russia's bombing in Syria.

Russia has accused Turkish President Recep Tayyip Erdogan and his family of helping IS through illegal oil trading, claims Ankara has strongly denied.

Russia's bombing in support of government forces in Syria is considered by the West as a threat to the high-profile peace negotiations that began in Switzerland this week.

The Syrian opposition's High Negotiations Committee has voiced outrage at an ongoing ­government offensive backed by Russian air power and called for a halt to airstrikes against civilians, among other demands.

Lavrov slammed "capricious people" in the Syrian opposition delegation, saying they were "starting to put forward preconditions" that had not been previously agreed, state news agency RIA Novosti reported.

The opposition delegation's demands "have nothing to do with the main principles of the Geneva Communique, Vienna documents and a UN Security Council resolution," ­Lavrov said, referring to key documents in the Syrian peace process.

Also on Wednesday, Syrian opposition chief Riad Hijab arrived in Switzerland, his grouping said. He went straight to meet other members of his High Negotiations Committee.