Update at 6:50 p.m. ET

U.S. officials have confirmed that a new round of airstrikes in Syria is ongoing, NPR Pentagon correspondent Tom Bowman told All Things Considered.

"We know some of the targets are oil assets, oil wells being controlled by the Islamic State. There's not a lot of detail at this time ... but it's likely around the Raqqah area, which is sort of [the Islamic State's] de facto headquarters."Rear Adm. John Kirby, the Pentagon spokesman, said that he can confirm U.S. military and Arab partner forces are undertaking additional strikes today against the Islamic State. No great detail yet, but we'll provide more detail later."

Oil and gas provide a big chunk of the Islamic State's revenues, and the U.S. is keen to dry up the group's finances.

Saudi Arabia and the United Arab Emirates participated in this round of attacks, which were conducted using jets and drones, according to a U.S. Central Command statement. The release described the targets as small, mobile refineries that produce 300-500 barrels of petroleum — as much as $2 million worth — each day.

Tom explains how these attacks fit into the larger conflict:

"Part of the effort is, of course, airstrikes — taking out command centers, taking out their oil refineries and their armor and some of their fighters. But the president said that this is a comprehensive effort; it's not just conducting airstrikes. ... They want to go after the financing of the Islamic State, so that's where these strikes come in, but they're also trying to prevent foreign fighters from coming into Syria. They're working with other countries on that. So that's part of the overall effort that they're putting together on these."

The Pentagon is still assessing the effectiveness of the airstrikes against the Islamic State in Syria, Tom says — both today's, and those from the initial attacks on Monday night.

Updated at 12:30 p.m. ET

Witnesses in eastern Syria near the Turkish border report a fresh round of airstrikes against Islamic State positions. The Pentagon has confirmed a new set of strikes, but a spokesman says the U.S. is not involved in any attacks near the Turkish border.

Using an alternate name for the extremist group, the U.S. Central Command said in a statement:

"U.S. military forces continued to attack ISIL terrorists in Iraq and Syria, using a mix of attack, bomber and fighter aircraft to conduct five airstrikes Tuesday and today."Two airstrikes west of Baghdad destroyed two ISIL armed vehicles and a weapons cache. Two airstrikes southeast of Irbil destroyed ISIL fighting positions. A fifth airstrike damaged eight ISIL vehicles in Syria northwest of Al Qa'im. All aircraft exited the strike areas safely."

NPR's Tom Bowman quotes Pentagon spokesman Col. Steve Warren as saying the U.S. does not know who if anyone is carrying out strikes near the Turkish border.

However, the other new strikes confirmed by the Pentagon come a day after the U.S. and five Arab allies carried out air and cruise missile attacks across northern Syria, targeting not only the self-declared Islamic State, also known as ISIS or ISIL, but also two other extremist groups — the Nusra Front and the largely unknown Khorasan group, which U.S. officials have said was planning attacks on U.S. and Western interests.

NPR's Dina Temple-Raston has a detailed Khorasan explainer here. And, The New York Times reports today: "American military and intelligence analysts were still studying damage reports from the initial air assault, but senior Obama administration officials expressed hope that they had killed Muhsin al-Fadhli, the leader of Khorasan and a onetime confidant of Osama bin Laden. The officials said they had been contemplating military action against Khorasan in recent months, but President Obama's decision to hit the Islamic State's forces inside Syria provided a chance to neutralize the other perceived threat."

On the latest attacks, The Associated Press says: "It was not immediately clear who carried out the airstrikes in and around Boukamal, the Britain-based Syrian Observatory for Human Rights said. But the activist group cited locals as saying the intensity of the air raids was similar to that of strikes on the town early Tuesday by the U.S.-led military coalition."

Reuters quotes Rami Abdulrahman, who runs the Syrian Observatory for Human Rights, as saying the border town of Albu Kamal and surrounding areas had been hit.

"Albu Kamal, on the main Euphrates River valley highway, is one of the most important border crossings between Iraq and Syria, along a frontier that Islamic State wants to erase after seizing territory on both sides and declaring a caliphate," the news agency says.

President Obama is set to address the United Nations General Assembly today to discuss, in part, the ISIS threat.

NPR's Michele Kelemen reports that the Security Council is expected to adopt a resolution to encourage countries to crack down on the flow of money to extremists and to encourage the prosecution of citizens who join terrorist groups.

The latest strikes also come as Britain's Prime Minister David Cameron could announce soon that his country will join in the airstrikes.

According to Reuters:

"Cameron is due to set out his position in a speech to the U.N. General Assembly in New York on Wednesday night at which he will call on the world to unite to destroy Islamic State (IS)militants, whom he has warned are planning to attack Britain."The decision to strike in Iraq would be at Baghdad's request. Cameron is due to meet Iraqi Prime Minister Haider al-Abadi on Wednesday. Sources in Cameron's office expect him to request British air strikes against IS during the meeting."

NPR's Ari Shapiro, reporting from London, says Iraq's President Fuad Masum is expected to ask for British military assistance and that Cameron will likely call for a vote in Parliament. Opposition leader Ed Miliband told the BBC he expects his party to support airstrikes against the group.

Meanwhile, the U.N. High Commissioner for Refugees said Turkey needs help urgently to deal with a sudden influx of more than 130,000 Syrian Kurds who have fled the fighting.

The BBC reports:

"On Tuesday, Turkish President Recep Tayyip Erdogan suggested Turkey could join military action against IS." 'We will give the necessary support to the operation. The support could be military or logistics,' " he told reporters in New York, where he is attending the UN General Assembly meeting."

The U.N. World Food Program is also warning that money needed to feed Syria is simply not there.

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