Damascus (AFP) - Syria condemned Wednesday's Turkish incursion into an Islamic State group-held border area as a "flagrant violation" of its sovereignty as Kurdish authorities said the action amounted to a "declaration of war".
The foreign ministry in Damascus said it "condemns the crossing of the Turkey-Syria border by Turkish tanks and armoured vehicles towards the Jarabulus area with air cover from the US-led coalition and considers it a flagrant violation of Syrian sovereignty".
The Syrian opposition in exile, however, welcomed the intervention.
The operation -- named "Euphrates Shield" -- began around 4:00 am (0100 GMT) with Turkish artillery pounding dozens of targets of the Islamic State (IS) jihadist group around Jarabulus, the Turkish prime minister's office said.
Turkish tanks and special forces accompanied by pro-Ankara Syrian rebels then rolled across the border in an unprecedented operation to drive IS out of Jarabulus, from which it has fired rockets into Turkey.
"Syria demands the end of this aggression," the foreign ministry said.
"Any party conducting a battle against terrorism on Syrian soil must do so in coordination with the Syrian government and the Syrian army who have been fighting this war for five years.
"Chasing out IS and replacing them with terrorist groups backed by Turkey is not fighting terrorism."
Turkish state media later reported that pro-Ankara Syrian rebels had reached the edge of central Jarabulus as part of the Turkey-led operation.
The semi-autonomous Kurdish administration, which controls much of the border regions in north and northeast Syria, angrily branded Turkey's intervention a "declaration of war".
"The Turkish government has abandoned its policy regarding the (Syrian) regime and now finds itself on the same side," it said in a statement.
The Istanbul-based opposition National Coalition, however, hailed the Turkish intervention and stressed that rebel forces were doing the fighting on the ground.
It issued a statement welcoming "the support of Turkey and the international coalition for the military operation in Jarabulus", in which "the rebels are carrying out the combat operations".
Turkey's incursion is its first into Syria since February 2015, when hundreds of Turkish troops crossed the border to move the relics of the grandfather of the founder of the Ottoman Empire.
In Ankara on Wednesday, visiting US Vice President Joe Biden said Washington had made it clear that Kurdish-led forces in Syria must not deploy west of the Euphrates River.
"We have made it absolutely clear... that they must go back across the river," Biden said at a news conference with Turkish Prime Minister Binali Yildirim.
"They cannot, will not and under no circumstances (will) get American support if they do not keep that commitment. Period."
Turkey fears that Syrian Kurds may have designs on Jarabulus after seizing the strategic Manbij area in northern Syria from IS.
Turkey sees the Syrian Democratic Forces (PYD) and its armed wing YPG as an extension of the outlawed Kurdistan Workers' Party (PKK) which has waged a bloody campaign against the Turkish state.