Turkish tanks and hundreds of opposition fighters thrust deep inside Syrian territory on Wednesday in a lightning operation that within hours pushed Islamic State of Iraq and the Levant (ISIL) fighters out of a key Syrian border town.

The air and ground offensive - the most ambitious launched by Ankara in the Syria conflict - made rapid progress towards Jarablus throughout the day, as rebel fighters captured ISIL-held villages surrounding the strategic border town.

"Jarablus can now be considered fully liberated," Ahmed Othman, a commander in the Free Syrian Army, told Al Jazeera from the scene, while another rebel spokesman said ISIL fighters had fled towards al-Bab to the southwest.

"The attack started in the morning and we were able to take control of a number of villages near the town. After a few hours and after controlling the hills surrounding the town, ISIL felt the danger. A large number of ISIL fighters withdrew south towards al-Bab, which is still under [ISIL, also known as ISIS] control."

Jarablus, a strategic town on the border with Turkey, had been controlled by ISIL fighters for two years. The group is now left with only one stronghold in Syria's northeast - al-Bab.

In a press conference on Wednesday, Turkish President Recep Tayyip Erdogan said the operation was also targeting Kurdish militia fighters - strongly opposed by Ankara but backed by the US as a key ally in the war against ISIL - who had also been closing in on Jarablus.

"We have said 'enough is enough' ... This now needs to be resolved," Erdogan said.

Joe Biden, the US vice president who met Erdogan in Ankara on Wednesday, reassured Turkey that Washington had instructed the Kurdish YPG that crossing west of the Euphrates River could mean the total loss of American support.

"They cannot, will not and under no circumstances get American support if they do not keep that commitment. Period," he said.

The Turkish government has accused the YPG of being an extension of the outlawed Kurdistan Worker's Party (PKK). The Turkish state has waged war against the separatist group for more than 20 years.

"The YPG has been the US-led coalition's strongest ground partner in the war against ISIL, but Turkish leadership wants the US to sever ties with the Kurdish faction," said Al Jazeera's Hashem Ahelbarra, reporting from Gaziantep on the Turkish side of the Syria-Turkey border.

Rapid advance

Wednesday's operation - named "Euphrates Shield" - began at around 4am (01:00 GMT) with Turkish artillery pounding dozens of ISIL targets around Jarablus.

Turkish F-16 fighter jets, backed by US-led coalition planes, also hit targets inside Syria.

A dozen Turkish tanks then rolled into Syria in support of Syrian opposition fighters who had also crossed, with as many as 5,000 rebel fighters - including groups such as the Turkmen Sultan Murat Brigade, Sukur al-Jebel, Sham Front and Feylek al-Sham.

The rapidity of the advance was in complete contrast to the long-grinding battles where Kurdish forces had taken towns in northern Syria such as Kobane and Manbij from ISIL.

As well as tanks, an AFP photographer in the area of Karkamis, opposite Jarablus, saw several smaller military vehicles believed to be carrying the pro-Ankara Syrian rebels.

Security sources quoted by Turkish television said a small contingent of special forces had travelled into Syria to secure the area before the larger ground operation.

Turkey wants to show it is serious about taking on ISIL, which has been blamed for a string of attacks inside the country, including a recent attack on a Kurdish wedding in Gaziantep that left 54 people dead, many of them children.

Ankara was long been accused of turning a blind eye to the rise of ISIL in Syria and even aiding its movements across the border, claims the government had always vehemently denied.

READ MORE: YPG launches assault to take all of Syria's Hasaka

Earlier this month, a coalition of primarily Kurdish fighters led by the YPG pushed ISIL fighters out of Manbij, a strategic city that lies west of the Euphrates river.

Saleh Muslim, head of the Democratic Union Party (PYD), the YPG's political wing, tweeted that Turkey was now in the "Syrian quagmire" and would be "defeated" like ISIL.

But a senior US administration official told AFP that Washington had already been "syncing up" with Turkey for Wednesday's operation and US advisers had been involved in a planning cell.

The Turkish air strikes were the first since a November crisis with Russia sparked when the Turkish air force downed one of Moscow's warplanes.

A dozen ISIL targets were destroyed in Wednesday's air strikes. Turkish artillery meanwhile destroyed at least 70 ISIL targets, according to Turkish television.

READ MORE: Almost 18,000 died in Syria's prisons, says Amnesty

The movements come at a critical juncture for Turkey in Syria's five-and-a-half-year war, and there are growing signs that Ankara is on the verge of a landmark policy shift.

Turkey has continuously called for the removal of President Bashar al-Assad, putting Turkey at odds with the embattled leader's main supporters - Iran and Russia.

But Turkish Prime Minister Binali Yildirim acknowledged for the first time over the weekend that Assad was one of the "actors" in Syria and may need to stay on as part of a transition.

In a note of discord after news broke of the Turkish-backed operation on Wednesday, Russia said it was "deeply concerned" by the situation on the border and warned of a "further degeneration of the situation".

Assad's government - which has has little control of country's northeast since 2012 - condemned the incursion as a "flagrant violation" of its sovereignty.