WRAPUP 11-Iran's Mousavi says ready for "martyrdom"-ally

* Mousavi says ready for 'martyrdom' - ally

* Mousavi calls for national strike if he arrested-witness

* Suicide bomber at Khomeini shrine

* Police fire teargas, use batons, water cannon

EDITORS' NOTE: Reuters and other foreign media are subject to Iranian restrictions on their ability to report, film or take pictures in Tehran.

(Adds Obama call to Iranian government)

By Parisa Hafezi

TEHRAN, June 20 (Reuters) - Opposition leader Mirhossein Mousavi said he was "ready for martyrdom", according to an ally, in leading protests that have shaken the Islamic Republic and brought warnings of bloodshed from Iran's Supreme Leader.