An Iranian newspaper, Khordad, renowned for its outspoken criticism of the conservative clergy has been attacked by unidentified assailants.

The official news agency said two men on a motorbike threw a stun grenade at the newspaper'soffices in Tehran, shattering windows and slightly injuring two reporters.

An anonymous phone caller said that next time it would be a bomb.The editor said the paper would come out as usual on Tuesday.

The newspaper was launched about two months ago by the former Interior minister, Abdollah Nouri, who angered conservatives in the government by supporting social and political reforms and was removed from office.

The attack comes at a time of increasing tension between moderates loyal to President Khatami and the conservatives.