Washington: US Secretary of State John Kerry called his Russian counterpart Sergei Lavrov on Thursday to express concern about a visit to Moscow by the commander of Iran's covert forces, a senior State Department official said.

General Qassem Suleimani, head of the Iranian Revolutionary Guards Corps' foreign operations, reportedly visited Russia late last month despite being subject to UN-backed international sanctions.

A State Department spokesman said today the United States had confirmed the trip had taken place and said US officials would raise their concerns with Russia at an upcoming New York meeting on violent extremism.

"Secretary Kerry also raised his concerns about the travel to Moscow by IRGC Commander Qassem Suleimani," the senior official said Thursday, outlining a call between the two diplomats.

Suleimani is one of several Iranian officials targeted by a 2007 United Nations travel ban because of their alleged links to Iran's nuclear or ballistic missile programs.

Despite the recent deal struck by Iran and world powers on its nuclear program the targeted sanctions against Suleimani and many of his colleagues remain in effect.

Suleimani has also been sighted visiting Iranian-backed forces in Iraq, Shiite and Kurdish units fighting the Islamic State jihadists group alongside government forces.

Iran also provides military support to Syrian President Bashar al-Assad's regime, which is embroiled in a four-year-old conflict with various rebel groups, and to the Lebanese Shiite armed movement Hezbollah.

Suleimani is considered a key figure in the provision of that military assistance.