Syrian and Iraqi terrorist forces obtained significant numbers of tanks, trucks, and U.S.-origin Humvees in recent military operations in Iraq and those arms are being shipped to al Qaeda rebels in Syria, according to U.S. officials.

U.S. intelligence agencies reported this week that photos of the equipment transfers were posted online by the Islamic State of Iraq and the Levant (ISIL), also known as ISIS, the ultra-violent terror group that broke away from al Qaeda but shares its goals and philosophy.

Pentagon spokesman Cmdr. Bill Speaks confirmed the weapons transfers and expressed concerns about the captured arms.

"We're aware of reports of some equipment—namely Humvees—and the pictures that have been posted online," Speaks said in an email. "We are certainly concerned about these reports and are consulting with the Iraqi government to obtain solid confirmation on what assets may have fallen into ISIL's hands."

Speaks added that the loss of the equipment to the terrorist group is "really a matter for the Iraqi government to speak to publicly" because "it is their equipment."

Exact numbers of captured arms and equipment are not known. The insurgents raided all the arms depots and vehicles belonging to Iraq’s Second Division, based in Mosul, which included a motorized brigade and several infantry brigades.

A defense official warned that ISIL claims that they have captured advanced weaponry, such as Blackhawk helicopters, are suspect.

"We do know that they made false claims last week, particularly with Blackhawk helicopters, which have never been sold to Iraq," the official said.

The seized weapons are said to include Russian-made T-55 tanks and one report said U.S. M-1 Abrams tanks were taken. Numerous Humvees were shown on flatbed trucks being transported from the Nineveh province, in northwestern Iraq, to ISIL-controlled areas of Syria, including the Al Shadadi area and the town of Tall Hamis.

The ISIL notified people in the region where the tanks were seen to be alert for possible U.S. airstrikes, presumably against the captured weaponry.

One online posting by ISIL fighters showed a captured Iraqi T-55 tank reportedly in Deir ez-Zor, Syria.

Other online photos of captured Iraqi military equipment showed towed artillery, trucks, and troop transports being transferred to Syria from Iraq.

The weaponry is expected to provide ISIL with a major advantage over other rebel groups in Syria in their civil war with the forces of the Bashar al Assad regime in Damascus, as well as against other rival rebel groups, including the official al Qaeda affiliate, Al Nusra Front.

In a statement posted through its Twitter account, ISIL on June 12 provided a "field report" with photos of its capture of Iraqi weapons and conquests of Iraqi military outposts.

The weapons were taken from military bases on the border with Syria and moved to areas in Syria controlled by ISIL that the group is calling its "caliphate."

One photo carried a caption in Arabic that read "Transferring the spoils to the Islamic State's headquarters in Wilayah [territory under the Islamic caliphate] Al-Barakah" in the Al Hasakah province in northeastern Syria.

A U.S. official familiar with intelligence assessment of the ongoing conflict in Iraq said the ISIL has seized key cities, including Mosul and Tikrit, but is not expected to attempt a further drive to the capital of Baghdad, which is more heavily defended.

Iraqi military forces, many of them trained by the U.S. military prior to the pullout of forces in December 2011, suffered widespread desertions during the ISIL invasion. Iraqi special operations forces, however, are said to be engaged in fighting the terrorist group.

Fighting continued in northern Iraq as ISIL fighters, estimated to include around 10,000 insurgents, sought to take the northern Iraqi town of Tal Afar, a strategic location sought for the group’s effort to maintain control and open a supply corridor between Syria and the areas of central and western Iraq not controlled by ISIL.

Iraqi forces retook some areas but the ISIL now has control of several areas and has a land corridor leading to Syria.

Bill Cowan, a former Army Special Forces officer and former defense contractor in Iraq, said the ISIL operation succeeded in seizing arms and equipment.

"The ISIL has got lots of weapons now," Cowan said in an interview.

The U.S. military during the war engaged in large-scale intelligence gathering in Iraq but now is hamstrung in spying on ISIL by the lack spying resources. "We pulled all that out," Cowan said of the electronic and signals intelligence forces.

In other Iraq developments:

ISIL published gruesome photos showing mass executions of Iraqi soldiers captured during the incursion from Syria that began June 9. Beheadings and crucifixions of Iraqis by ISIL also were reported. The Twitter account that posted links to the photos was later removed.

Iraqi authorities blocked all social media services in an effort to thwart ISIL communications and propaganda. The blockage covered Facebook, Twitter, YouTube, and applications including WhatsApp, Viber, and Tango.

In Mosul, Iraq’s second largest city, ISIL ordered the demolition of all churches, as part of its scorched earth Islamist policy of imposing Sharia law.

The leader of Iran’s Islamic Revolutionary Guards Corps paramilitary unit known as the Quds Forces, Maj. Gen. Qassem Suleimani, is now assisting Iraq’s commanders in operations against ISIL, the Sunday Times reported, quoted an Iraqi official.

reported, quoted an Iraqi official. The State Department announced that it is withdrawing some staff at the U.S. Embassy in Baghdad. "U.S. citizens in Iraq remain at high risk for kidnapping and terrorist violence," the department said in a travel warning.

The Turkish and Iranian government are conducting military operations against militants in the mountain regions bordering Iraq, including troop deployments and artillery shelling.

The Pentagon announced the amphibious ship USS Mesa Verde is now deployed in the Persian Gulf for possible "quick reaction and crisis response operations." The ship, with Marine Corps MV-22 tilt rotor aircraft, joins the aircraft carrier USS George H.W. Bush in the gulf.

A report in the Arabic-language newspaper Al Hayah quoted Mosul residents who described the takeover of the city by ISIL.

Abu Ahmad, a former colonel in the Iraqi Army, described the initial stages of the ISIL attack as launched by "hundreds" of local militants wearing jeans and Arabic headscarves who struck on the night of June 9 and morning of June 10.

The first engagements were carried out with tanker truck bombs and other explosive devices set off at the entrances to military bases.

"At around 2200 [11:00 pm], I left my home on the [western] side, and found that the police were abandoning police stations, often without a fight, and before the arrival of the gunmen, and they announced to the public that they would prefer to sit at home than get into an armed confrontation with any party," Ahmad told the newspaper.

"The groups that entered the city wanted to release prisoners from the temporary detention centers of the police, and then crept northward toward the Badush central prison, and before midnight they captured the governor's office without firing a single bullet."

The initial group that took over Mosul included between 3,000 and 4,000 militants led by former senior officers of the Iraqi military.

A police officer in Mosul told the newspaper that forces of the Iraqi Army's Second Division abandoned the weapons and equipment, and withdrew from military camps around 11:00 pm.

Mosul International Airport also was seized without fighting. Three Russian-made Mi-17 helicopters used by Iraqi special operations forces were believed seized at the airport.

ISIL also attacked the prison in Mosul and freed numerous jihadists imprisoned at a transfer prison there. Guards at the prison reportedly abandoned the facility during the ISIL attack. Other area prisons also were opened as part of the ISIL.

An estimated 2,500 prisoners, many held on terrorism charges, were freed.