KAISERSLAUTERN, Germany — Chinese-made smartphones that the heads of U.S. intelligence have urged Americans not to buy are being sold to servicemembers across Germany at on-base exchange facilities.

The Huawei phones, which are being sold by TKS, an Army and Air Force Exchange Service concessionary and subsidiary of Vodaphone, could be used to gather sensitive information, according to U.S. intelligence agencies. They are banned for official government use in most cases.

The Defense Department asked whether Huawei mobile phones were being sold at exchange facilities but has not offered any other direction, said AAFES senior spokesman Chris Ward.

“We responded ‘yes' and have had no other inquiries,” Ward said in an email response. “Should there be an official determination made by law enforcement officials that these phones present a security risk, the Exchange will instruct its vendors to remove impacted products from their assortment.”

Officials at Ramstein Air Base, where Europe's largest exchange and a TKS concessionary operate, said they are aware that the phones are being sold on base.

Although officials did not address Huawei specifically, they said that servicemembers should adhere to operational security standards when they post anything online, take pictures or configure their location settings.

“Servicemembers need to pay attention,” said Lt Col. Joel Harper, 86th Airlift Wing spokesman. “Regardless of where the device is purchased, on base or off base, servicemembers should practice good (operational security).”

In February, the director of national intelligence, along with the heads of the CIA, FBI, National Security Agency, Defense Intelligence Agency and the National Geospatial-Intelligence Agency testified before a Senate committee that Americans should not use Huawei products because of the security risks they pose.

The concern about Huawei first focused on routers, switches and other high-bandwidth commercial products but later expanded to consumer mobile phones.

FBI Director Christopher Wray testified that Huawei products provide the Chinese government with the ability to maliciously modify or steal information and to conduct undetected espionage.

“We're deeply concerned about the risks of allowing any company or entity that is beholden to foreign governments that don't share our values to gain positions of power inside our telecommunications networks,” Wray said.

Huawei is also one maker of personal mobile internet modems, also called "pucks," which in recent years have been sold to U.S. troops at a coalition base near Irbil, the capital of Iraq's Kurdish region. Some soldiers may have purchased similar devices made by Chinese telecom company ZTE, which was sanctioned by the U.S. government for violating trade embargoes by sending U.S.-made components to Iran inside its devices.

Huawei is a private company started by a former People's Liberation Army officer.

U.S. intelligence officials say the company has very close ties to the national Chinese government. Spokesmen for the company have repeatedly denied claims their devices pose any security risks. The devices are used commonly throughout Europe.

Huawei has been the target of numerous U.S. regulations and laws meant to address national security concerns, such as a law in 2013 that required federal law enforcement agencies to sign off on certain purchases by government agencies of Huawei products.

New rules proposed by the Federal Communications Commission would bar U.S. telecommunications companies that receive FCC subsidies from buying products from foreign companies with security concerns.

Companies have yet to be named, but Huawei is expected to make the list of banned companies. A bill introduced in January by Rep. Michael Conway, a Republican from Texas, would make it illegal for U.S. government contractors to use any Huawei equipment.