TEHRAN, June 28 (RIA Novosti) - Police in Tehran have arrested eight Iranian nationals working at the British Embassy, on suspicion of "active" involvement in the recent post-election street riots, Iranian media reported on Sunday.

The arrests are likely to further damage relations between Iran and the United Kingdom, which have been strained by expulsions of diplomats and Iranian authorities' allegations that British government aided protests after the controversial June 12 presidential election.

Iran's state English-language Press TV cited "security officials" as saying the embassy employees had been arrested for "inflaming post-election tensions in the country."

The semi-official Fars agency cited an unnamed source as saying the employees "had a considerable role in recent unrest" and "were taken into custody."

President Mahmoud Ahmadinejad's landslide re-election sparked mass protests amid allegations of ballot fraud from the two main challengers, Mir Hossein Mousavi and Mehdi Karroubi.

At least 13 people were killed during the riots according to Iranian media, and over 450 arrested in the largest challenge to the Islamic Revolution since the 1979 overthrow of the U.S.-backed shah.

Despite the protests, Iran's Guardian Council, which oversees elections, rejected the opposition's calls to annul the results of the vote.