Syrian aircraft have bombed border areas between Syria and Iraq, killing three Iraq civilians according to local officials.
The bombings come as fighters from the Islamic State in Iraq and the Levant (ISIL) try to consolidate their hold over parts of the border separating the two countries.
Separately, Iraqi military officials denied on July 3 that the country's border guards had withdrawn from the frontier with Saudi Arabia.
The denial comes after Dubai-based broadcaster Al-Arabiyah reported that Riyadh had deployed 30,000 soldiers along the 800-kilometer border after Iraqi forces withdrew.
It aired a video showing Iraqi soldiers saying they were ordered to withdraw from the Saudi and Syrian borders due to the swift advances by Sunni-led insurgents.
Meanwhile, activists say ISIL fighters have taken control of Syria's largest oil field, near the Iraqi border.
The Britain-based Syrian Observatory for Human Rights said the Al-Qaeda splinter group captured the Al-Omar oil field in eastern Deir el-Zour Province on July 3 after a rival rebel group withdrew.
It said the Al-Qaeda-linked Al-Nusra Front left its positions without firing a shot.
By seizing the Al-Omar field, ISIL now controls most oil and natural-gas fields in Deir el-Zour.
ISIL has captured swaths of territory in eastern and northern Syria as well as northern and western Iraq.
It has declared the establishment of a caliphate and renamed itself the Islamic State.
In Washington, the U.S. military's top officer, Martin Dempsey, said on July 3 that Iraqi forces have strengthened their defenses around Baghdad and are capable of defending the capital.
But Dempsey, the chairman of the U.S. Joint Chiefs of Staff, said Iraqi forces would need outside help to eventually regain territory lost to Sunni militants.
Dempsey, who was speaking at a press conference at the Pentagon in Washington, also said the United States won't be involved in combat operations in Iraq.
That echoes U.S. President Barack Obama's recent statements.
Defense Secretary Chuck Hagel, speaking at the same news conference, said about 200 U.S. military advisers are now in Iraq.
He said they are assessing the situation as the Iraqi government seeks to counter the Islamic State of Iraq and the Levant.