Arbaeen marks 40th day of mourning for Imam Hussein (PBUH), the grandson of Prophet Mohammad (PBUH), which follows Ashura the anniversary of the martyrdom of Imam Hussein.
Iraqi government has formed a new cooperation room with the presence of Iraqi police, Iraqi national police, army and intelligence to provide the security for the program since ten days before Arbaeen, Press TV correspondent in Baghdad Wisam al-Bayati says.
According to al-Bayati, as the 10 million pilgrims have already arrived in the city for the event, the number of the pilgrims is expected to rise to 14 millions during the day.
Tens of thousands of Iraqi policemen and soldiers have been deployed in and around Karbala to thwart any possible insurgent attacks during the ceremony, after three straight days of attacks against pilgrims.
On Friday, a female bomber struck a tent filled with women and children resting during their pilgrimage, killing 40 people and wounding about 80, in the deadliest of the attacks.
On Thursday, a bomber had detonated an explosive belt packed with nails among worshippers in Karbala near Imam Hussein's shrine, killing eight pilgrims and wounding more than 50.
A day earlier, at least 12 people were killed and more than 40 wounded in bombings in Baghdad that targeted pilgrims traveling to Karbala.
Imam Hossein, the son of the first Imam, Ali, and the grandson of Prophet Mohammad, is the third Imam of Islam.
He fought against cruelty, corruption and injustice and was martyred in the course of his heroic struggle some 14 centuries ago.