Doug Stanglin and Ray Locker

USA TODAY

U.S. aircraft and those from Saudi Arabia and the United Arab Emirates struck Islamic State targets in Syria on Wednesday, including 12 oil refineries, the U.S. Central Command said.

The 13 airstrikes used a combination of fighter aircraft and drones, according to Central Command. The targets were in the remote eastern part of Syria near the towns of Al Mayadin, Al Hasakah and Abu Kamal. Another strike hit an Islamic State vehicle near Dayr az Zawr, also in eastern Syria.

The latest attacks follow strikes early Wednesday on five targets in Iraq and Syria connected to the Islamic State terrorist organization, also known as ISIL or ISIS, Central Command reported.

National security adviser Susan Rice told NBC News on Wednesday that the White House had seen social media reports that the allied airstrikes had killed the leader of the Khorasan terrorist organization, Muhsin al-Fadhli.

"We can't confirm that at this stage," Rice said, "but we've seen reports on social media to that effect. We will continue to look for signs as to whether or not that's, in fact, the case."

The Pentagon could not confirm whether al-Fadhli had been killed, a military official said on condition of anonymity because the official was not authorized to speak publicly.

"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," a Central Command statement says. "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 vehiclesin Syria northwest of Al Qa'im. All aircraft exited the strike areas safely."

The BBC quotes Syrian activists as reporting strikes around the Kurdish town of Kobane, close to the border with Turkey. The town has been besieged by Islamic State fighters for several days.

According to the BBC, witnesses said they saw two military aircraft approaching from Turkey, but Turkish officials denied its airspace or bases had been used in the attack.

Contributing: Tom Vanden Brook