ANKARA, Turkey (AP) — The Latest developments in the civil war in Syria (all times local):

7:45 p.m.

A U.S. defense official says that American planes are conducting airstrikes as part of the ongoing operation to drive Islamic State militants from the northern Syrian town of Jarablus.

The official says that U.S. A-10 and F-16 fighter jets are participating in the cross-border operation launched by Turkey and Syrian rebels groups on Wednesday.

The U.S. is also providing assistance with intelligence and surveillance aircraft overhead.

Syrian opposition forces say they are in control of the town but still battling pockets of IS fighters.

U.S. special forces have been working with the Syrian rebels. But U.S. defense officials say American commandos are not participating in the fight for Jarablus. The officials spoke on condition of anonymity because they weren't authorized to discuss the operation publicly.

— Lolita C. Baldor in Washington

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7:15 p.m.

Syrian opposition forces say they are in control of Jarablus only hours after Turkey launched a cross-border operation to help them oust the Islamic State group from the border town in northern Syria.

Several rebel factions involved in the fighting announced they had liberated the town from IS, but were still fighting small pockets of militants.

The Britain-based Syrian Observatory for Human Rights, which monitors the Syrian civil war, says rebels are in almost full control of Jarablus, adding that IS had lost its last link to the outside world.

Ahmad al-Khatib, an opposition media activist embedded with the rebels, says they control 90 percent of the town and posted photos of rebels purportedly in the town's center.

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6:45 p.m.

Russia has expressed deep concern about Turkey's ground incursion into Syria, saying it raises the risk of civilian casualties and the worsening of ethnic tensions between Kurds and Arabs.

The Russian Foreign Ministry statement issued Wednesday says Moscow believes the Syrian crisis can be resolved only on the basis of international law through dialogue involving all ethnic groups, including the Kurds.

While Moscow has supported Syrian President Bashar Assad in Syria's civil war, carrying out air strikes in support of government troops, Ankara has backed the rebels fighting Assad.

Turkey's operation on Wednesday targeted the Islamic State-held border town of Jarablus, but also appears aimed at preventing Syrian Kurdish forces — who have been among the most effective opponents of IS — from expanding further across northern Syria.

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6 p.m.

A spokesman for a Syrian rebel group taking part in the Turkish-backed operation to clear Islamic State militants from a key border town says rebel fighters have entered the town.

Captain Abdel-Salam Abdel-Razzak, spokesman for the Nour al-Din al-Zinki rebel group, tells The Associated Press that the fighters on Wednesday were combing Jarablus for "pockets" of IS militants.

A media opposition activist embedded with the rebels says fighters are inside the town, adding that they are facing very limited resistance from the militants.

Ahmad al-Khatib says IS fighters withdrew to the IS-held town of al-Bab south of Jarablus and neighboring villages following intense Turkish shelling.

The Turkish state-run Anadolu Agency also reported that Syrian opposition forces have reached the entrance of Jarablus.

CNN Turk aired footage of what it said were Syrian opposition fighters in the Jarablus town center, which appeared to be deserted.

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5:30 p.m.

A senior U.S. administration official says U.S. advisers have been working closely with Turkey on plans for the operation launched against an Islamic State-held border town.

The official says the U.S. has been providing intelligence and air cover in an effort to soften up targets to aid the operation to retake Jarablus, which began early Wednesday.

The official was not authorized to discuss the military operations publicly and spoke on condition of anonymity.

Both Turkish and Syrian government officials say the cross-border operation was aided by U.S. airstrikes.

— Kathleen Hennessey in Washington

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5:15 p.m.

U.S. Vice President Joe Biden is calling on Syrian Kurdish forces to move back across the Euphrates River, telling them they will lose U.S. support if they don't.

Speaking at a press conference in Ankara on Wednesday, Biden says Kurdish forces "must move back across the Euphrates River."

He says "they cannot — will not — under any circumstance get American support if they do not keep that commitment."

Biden indirectly expressed support for the Turkish operation launched Wednesday to clear Islamic State militants from the town of Jarablus and deter Kurds from further expanding in northern Syria.

Turkish state media says Syrian opposition forces backed by Turkey have reached the "entrance" of Jarablus, which lies on the last main supply line between IS territory and the border.

The U.S.-backed Kurdish forces seized the border town of Manbij from IS militants earlier this month. Turkey said they had to retreat after clearing it from IS.

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2:20 p.m.

Syria's government has denounced Turkish military incursion, describing it as Turkey's "blatant violation" of Syrian sovereignty.

In a statement reported by state-run news agency SANA on Wednesday, the government says that "any move to combat terrorism on Syrian territories should have been coordinated with the Syrian government and army."

The statement also calls for an immediate end to the Turkish "aggression," which it says is being carried out under the pretext of fighting terrorism.

It says: "Fighting terrorism cannot be undertaken by ousting Daesh and replacing it with other terrorist organizations directly backed by Turkey." Daesh is the Arabic language acronym for IS.

The statement added that Turkish tanks and armored personnel carriers crossed into Syria earlier in the morning, under the cover of U.S.-led coalition airstrikes.

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1:40 p.m.

Turkey's state-run news agency says Syrian rebels have captured a village from the Islamic State group near the IS-held border town of Jarablus in a joint push with Turkey's military.

The Anadolu Agency, citing unnamed military officials, says the Syrian opposition fighters took the village of Kaklijeh with the support of Turkish armored units.

Anadolu says the village is some 3 kilometers (1.8 miles) away from the Turkish border. It says Turkish warplanes and artillery were also pressing ahead with their attacks against IS targets.

The report also says the rebel forces are expected to advance toward Jarablus backed by the Turkish armored units.

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1 p.m.

Turkey's state-run news agency says that police teams have mounted simultaneous raids at multiple locations in Istanbul to detain several suspected members of the Islamic State group.

The Anadolu Agency reports the operations took place early on Wednesday in two Istanbul districts and were coordinated by a helicopter flying overhead.

The operation comes days after a suspected IS bombing at a wedding in southeast Turkey killed at least 54 people. It also coincides with a Turkish military incursion into Syria to clear a border town of the IS group.

Several suspects were detained and their addresses searched. Authorities did not disclose the number of those detained.

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12:40 p.m.

The Turkish president says his country's military operation in Syria aims to prevent threats from "terror" groups, including the Islamic State and a Syrian Kurdish militia that is affiliated with Turkey's outlawed Kurdish rebels.

Recep Tayyip Erdogan says Wednesday's operation was launched in response to a string of attacks in Turkey, including a suicide bomb attack at a wedding party near the border which killed 54 people.

He says no one should consider "the Syrian issue to be independent from Turkey's domestic issues."

Erdogan, addressing groups that have targeted Turkey, says: "You will not succeed. You will not divide our nation, you will not lower our flag, you will not tear up our motherland, you will not topple our state."

He also added: "You will not silence our calls to prayer, you will not make this country kneel, you will not chain this people."

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11:55 a.m.

A Syrian activist group monitoring the civil war says Syrian rebels who were amassed at the Turkish border have crossed into Syria as part of a Turkey-backed operation to liberate an Islamic State-controlled border town.

The Syrian Observatory for Human Rights says the fighters were preceded by Turkish tanks and mine sweepers that crossed into Syria earlier on Wednesday as part of the operation to clear Jarablus from IS militants.

The Britain-based monitoring group didn't say how many fighters were involved. On Tuesday, it said that around 500 rebels were waiting to cross into Syria.

Turkish state media, meanwhile, say the rebels were about to enter a Syrian village leading to Jarablus.

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11:30

Turkey's state-run news agency says Turkish tanks have crossed into Syria as part of a military operation to free a border town held by the Islamic State group.

In its report, Anadolu Agency, which cited unnamed government officials, did not say how many tanks had entered Syria.

Turkeys' private NTV television says as many as 20 tanks had crossed into Syria. It said clashes were taking place at the border.

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11 a.m.

Vice President Joe Biden has arrived in Ankara for talks with Turkish leaders as Turkey launched a military operation to clear a Syrian border town of Islamic State militants.

Wednesday's visit comes at a difficult time for ties between the two NATO allies.

Turkey is demanding that Washington quickly extradite a U.S.-based cleric blamed for orchestrating last month's failed coup. The United States is asking for evidence against the cleric and asking that Turkey allow the extradition process to take its course.

In Syria, Turkey is concerned about the growing power of U.S.-backed Syrian Kurdish forces, who it says are linked to Kurdish groups waging an insurgency in southeastern Turkey.

Wednesday's operation puts Turkey on track for a confrontation with the Kurdish fighters in Syria.

Biden is scheduled to meet with Turkish President Recep Tayyip Erdogan and Prime Minister Binali Yildirim.

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10:35 a.m.

Turkish Interior Minister Efkan Ala says Turkey launched the operation to free the IS-held Syrian town of Jarablus to safeguard its own security.

The minister says Turkey "cannot sit and watch" and that "it is Turkey's legal right, it is within its authority" to take action.

The minister added that Wednesday's operation aimed to support the moderate Syrian opposition and is being carried out in coordination with the U.S.-led coalition forces. He said he hoped the operation to clear Jarablus would be completed at the soonest, but did not provide a time-frame.

About the operation's duration, he says: "Until when? Until this threat is removed and the terror threat on our border disappears."

Ala also says that his country "will not provide the opportunity for terror organization to threaten Turkey from across the border," adding that the Turkish town of Karkamis, across the border from Jarablus, had been hit by nine mortar rounds on Tuesday and another round on Wednesday.

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9 a.m.

A Turkish media report says a small number of Turkish special forces have crossed into Syria as part of a Turkish operation to rid a Syrian border town of Islamic State group militants.

Private NTV television says the Turkish special forces entered Syria on Wednesday in what it described was an "intruder mission" to carry out "pinpoint operations" against IS as part of the mission to clear the town of Jarablus of the extremists.

The London-based Syrian Observatory also said the Turkish troops had entered Syria.

Turkish government officials could not immediately confirm the report.

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5 a.m.

Turkey's and the U.S.-backed coalition forces on Wednesday launched an operation to clear a Syrian border town from Islamic State militants, the office of the Turkish prime minister said.

The operation began at 4 a.m. (0100 GMT), with Turkish artillery launching intense cross-border fire on the town of Jarablus, followed by Turkish warplanes bombing IS targets in the town, the state-run Anadolu Agency reported.

It was not immediately clear if any Turkish or Turkish-backed Syrian opposition forces crossed the border to take part in the operation.

The news agency said the operation aims to clear Turkey's border of "terror organizations" and increase border security, as well as "prioritize and support" Syria's territorial integrity. The assault followed Turkish Foreign Minister Mevlut Cavusoglu pledge on Tuesday of "every kind" of support for operations against IS along a 100-kilometer (62-mile) stretch of Syrian frontier.