(CNN) -- Syrian state-run television reported Thursday that forces loyal to President Bashar al-Assad killed three Westerners, including an American woman and a British citizen, who it claims were fighting with the rebels and were found with weapons.
Syrian TV identified the woman, releasing what it claimed were images of her Michigan driver's license and U.S. passport. It also released what is said was the name and passport of a British citizen. It did not identify a third person who it claimed was a Westerner.
The report said the three were ambushed in their car in the flashpoint province of Idlib in northwestern Syria, where government forces have been battling rebels for control.
TV footage showed a bullet-riddled car and three bodies laid out. It also showed weapons, a computer, a hand-drawn map of a government military facility and a flag belonging to the al Qaeda-affiliated al-Nusra Front.
The United States is aware of the claim that an American woman was killed and is working through the Czech Republic mission in Syria to obtain more information, a State Department official, speaking on condition of anonymity, told CNN.
Citing privacy concerns, "we are unable to comment further," the official said.
A family member of the American woman told CNN on Thursday she was informed by the FBI about the death. The family member said the FBI did not provide any details about how the woman died.
CNN is not identifying the family member, who lives in Michigan, until next of kin notifications have been completed.
The UK Foreign Office said it was aware of the claims, but is not able to verify them without further information.
If the Syrian state TV report is true, it will not be the first time an American has been accused of fighting with rebel groups to overthrow al-Assad.
In March, a former U.S. soldier was arrested and charged by the U.S. government with illegally using a weapon on behalf of the al-Nusra Front.
Eric Harroun, 30, of Phoenix, was arrested by the FBI after returning to the United States from Syria, where authorities allege he fought with the militant group. He was charged with the alleged use of a rocket-propelled grenade.
The organization he allegedly fought with, al-Nusra Front, is linked to al Qaeda in Iraq. Al-Nusra has claimed responsibility for more than 600 attacks in Syria, the Justice Department said.
An FBI affidavit says Harroun crossed into Syria in January 2013 and fought against al-Assad's forces. He posted photos and videos of himself on the Internet handling RPGs and other weapons, it said.
Harroun served with the U.S. Army from 2000 to 2003.
The report by Syrian state TV came on the same day that a leader of Syria's main rebel coalition said the group may not participate in a conference aimed at brokering an end to the civil war.
"It is difficult to continue when Syrians are constantly being hammered by the Assad regime with the help of outside forces," said George Sabra, acting chairman of the National Coalition, in a statement.
He cited the siege of Qusayr and attacks on Eastern Gouta, a suburb of Damascus, as well as what he said was an "invasion" by Iranian militia members in support of al-Assad.
Russia, which supports Damascus, expressed its own reservations. Conditions on the peace talks demanded by the National Coalition are too restrictive, Russian Foreign Minister Sergei Lavrov told reporters, state news agency ITAR-Tass reported.
"One has the impression that the National Coalition and its regional sponsors are doing their utmost in a bid to prevent the beginning of a political process and resort to all means, including brainwashing in the West, to induce military intervention," Lavrov is quoted as saying. "We regard such approaches as impermissible."
In addition, the coalition "is not the sole representative of the Syrian people," Lavrov said. "The coalition has no constructive platform."
The National Coalition has demanded that al-Assad step aside as a condition for its participation in the talks, which were originally scheduled to be held this month in Geneva, Switzerland, but have been delayed.
The Syrian government has insisted that any talks be held without preconditions and has said that al-Assad will finish his term and must be qualified to run again in the 2014 elections.
Fighting rages on
Some 3,000 to 4,000 Lebanese Hezbollah fighters have been deployed to Syria, where they are fighting alongside government forces, French Foreign Minister Laurent Fabius told the Foreign Affairs Committee of France's National Assembly.
The Lebanese fighters have been involved in a battle for Qusayr, a town of about 20,000 that sits astride one route to the Syrian coast and another to the Lebanese border.
For the rebels, holding Qusayr represents a way of limiting the regime's ability to sustain itself.
On Thursday, the media office of the Syrian Coalition in Istanbul, Turkey, said in an appeal for help that the number of wounded citizens in Qusayr had exceeded 1,000.
The state-run Syrian Arab News Agency said the fighting was part of its mission "to pursue terrorists in Qusayr and its countryside."
In an interview broadcast Thursday night by the Hezbollah television station Al-Manar, al-Assad was quoted by Lebanese media as saying, "Syria and Hezbollah are one axis."
Hezbollah forces "are in Lebanon and Syria, on the border area," al-Assad said.
According to the pro-Hezbollah Al-Akhbar newspaper, he said, "There are groups of (Hezbollah) party fighters in the border areas with Lebanon. But the Syrian army is the one fighting and running battles against the armed groups, and will continue in this battle in order to eliminate" what he described as "terrorists."
The president expressed skepticism that the talks proposed for Geneva would prove fruitful, the newspaper reported.
Al-Assad is further quoted as saying that "Syria received the first batch of the Russian S-300 missiles, antiaircraft systems" and that "the rest of the shipment will arrive soon."
"The contracts are not related to the conflict," he said. "We negotiate with them for various kinds of weapons for years. And Russia is fulfilling these contracts."
Russia has been criticized by the West for reported sales of six S-300 air defense systems to Syria under a 2010 contract.
Moscow, however, has said such deliveries would conform with international law and has denied supplying Syria with weapons that can be used against civilians.
CNN's Stephanie Kotuby, Brian Todd, Tom Watkins, Amir Ahmed and Saad Abedine contributed to this report.