The US State Department has seized the passport of former Marine and UN weapons inspector Scott Ritter, he told RT on Monday.

Ritter was on his way to Russia for the St. Petersburg International Economic Forum (SPIEF) when he was pulled off the plane and had his documents confiscated.

"I was boarding the flight. Three [police] officers pulled me aside. They took my passport. When asked why, they said 'orders of the State Department'. They had no further information for me," Ritter told RT. "They pulled my bags off the plane, then escorted me out of the airport. They kept my passport."