Opposition representatives in Iran have called on President Khatami to order an investigation into the disappearance of an opposition activist two months ago.

In a letter, nearly one-hundred members of the banned Freedom Movement of Iran say there's been no information on the man, Parviz Davani, a left-wing activist who disappeared after publishing a bulletin criticising the government.

The appeal follows the suspicious killing of three Iranian dissidents this week.

Correspondents say violence against the opposition, commonplace before the election of Mr Khatami last year, has been on the increase in Iran, reflecting the continuing political struggle between the moderates and conservatives in the Iranian leadership.