KABUL (Reuters) - Millions of Shi’ite Muslims performed mourning rituals on Thursday to mark Ashura, the holiest festival in their calendar, amid heightened measures in many places to protect against sectarian attacks.

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Red and green banners fluttered in Shi’ite neighborhoods in Kabul, the Afghan capital, while armed volunteer groups stood guard at mosques and major intersections.

Attacks in recent years targeting the country’s mainly Shi’ite Hazara minority have been claimed by an affiliate of Islamic State, and worsening security has led to a sharp reduction in large public gatherings.

In Bangladesh, a majority Muslim nation of 160 million, where Islamist militants have targeted Shi’ite shrines and mosques over the past few years, authorities said they had tightened security.

“Although there is no specific threat, we have taken all possible measures to avoid any unexpected incidents,” said Asaduzzaman Mia, the chief of metropolitan police in Dhaka, the capital.

Ashura falls on the 10th day of the lunar calendar month of Muharram and commemorates the martyrdom in 680 AD of Imam Hussain Ibn Ali, one of the grandsons of the Prophet Mohammad, near Karbala in what is now Iraq.

Shi’ites mark the festival with large public rituals, sometimes involving bloody self-flagellation or cutting to signify a link with the sufferings of Hussain, whose death symbolizes a wider struggle against oppression and tyranny.

“It is not just a ritual, but also an occasion to confess the mistakes we have made in the past,” said Humayan Kabir, a Shi’ite Muslim in the old part of Dhaka.

The death of Hussain eventually led to the division of Islam into the two main Sunni and Shi’ite sects and in recent years, the festival has been scarred by bloody sectarian attacks in many countries.

In India, Shi’ites were making preparations to mark the festival on Friday, in line with the customary sighting of the moon.

“We enact the battle of Karbala and want to show that if we had been there we would have fought alongside Hussain and his family,” said Nasir Hussain, a resident of the disputed Himalayan region of Kashmir.

Mourners will gather in the financial capital of Mumbai on Thursday for a pre-Ashura procession during which they whip themselves, walk over burning coals and perform with fire.

“The stand that Imam Hussain took all those years ago reinforces my belief in the goodness of society,” said Najaf, a mourner in India’s southern tech hub of Bengaluru.

“It reminds me to fight for my beliefs no matter what. He lost the battle, but what he fought for still holds true to this very day.”