The Ashura is observed on 10th day of Islamic of Muharram, falling tomorrow, to commemorate the martyrdom of Hussain Ibne Ali, the grandson of Prophet Mohammad.
The Shiites have taken out processions in major cities on 9th day of Muharram today.
In Pakistan's most populous province of Punjab, at least 12 districts including Lahore and Rawalpindi, were declared sensitive, said the Inspector General Police (IGP) Mushtaq Sukhera.
Entries to the route of procession have been strictly monitored with the help of walk-through gates and metal detectors. CCTV and drone cameras are being used to record the movements of people.
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In Pakistan's biggest city of Karachi, additional IG police Mushtaq Mehr was personally supervising the security arrangements of the processions and gatherings.
He said about 28,000 security persons were taking care of security of Karachi.
Thousands of more security personnel were deployed at other places in Sindh province.
DIG of Quetta Imtiaz Shah said that more than over 5,000 security personnel were guarding the capital Quetta which has a history of attacks at Shiite shrines.
In the militancy-plagued Khyber Pakhtunkhwa province, police, paramilitary Frontier Corps and army was deployed to assure security.
The police has also declared Hangu, Kohat and Dera Ismail Khan as the most sensitive districts.
Police has also banned the entry of Afghan nationals in provincial capital Peshawar and also banned pillion riding in the city.
Shiite are attacked by extremist Sunni groups who consider them as heretics.