Iraqi authorities have closed a major shrine in Baghdad's Kadhimiya area to women amid security concerns as a Shia religious ceremony reaches its climax.
Ashura is among the holiest days for Shia Muslims, but women will be barred from the Imam Moussa al-Kadhim shrine.
At least 35 people were killed there by a male suicide bomber on Sunday. Early reports said the bomber was a woman.
Correspondents describe the ban as an extraordinary step, driven by deep concerns over security.
The security forces in Iraq lack female members, allowing women to go unsearched and thus able to penetrate security cordons, says the BBC's Jonny Dymond in Baghdad.
Heavy security is also in place in the city of Karbala, south of Baghdad, where shrines to relatives of the Prophet Muhammad are housed.
Hundred of thousands of Iraqi and foreign pilgrims have streamed into Karbala for the religious event.
An estimated two million pilgrims are being watched over by nearly 30,000 members of the security forces there.
Some Shia pilgrims will flagellate themselves with chains or knives in memory of the Imam Hussein, grandson of the Prophet Muhammad, who fell at the battle of Karbala 14 centuries ago.