Tribute to Khomeini?

From earlier today from Tehran:

“Minutes ago, a terrorist detonated his explosive vest in the Imam Khomeini shrine. The blast caused damage in one section of the shrine,” Iran’s deputy police chief for operations, Hossein Sajedinia, was quoted as saying by Mehr [news agency].

Blame hasn't been clearly attached. However, it's reasonable to doubt that the pro-democracy activists were involved.