Washington, Oct 21 (DPA) The US Tuesday called for the immediate release of an Iranian-American citizen who was sentenced to a 12-year prison term in Iran, declaring the charges against him are “groundless”.

“Given the groundless nature of charges against him, we call on Iran to grant his immediate release,” State Department spokesman Ian Kelly said.

An Iranian court sentenced Kian Tajbakhsh to prison after the scholar was convicted of participating in the unrest following the controversial June presidential election.

Tajbakhsh was arrested in July during a demonstration protesting the re-election of President Mahmoud Ahmadinejad. He was accused of seeking to topple the Islamic government.

Tajbakhsh is among several US citizens detained by Iranian authorities.