Ko Ni, a respected legal adviser to the ruling National League for Democracy, was shot in the head on Sunday afternoon as he waited outside Yangon airport while holding his grandson.
While assassinations of political figures in Yangon are rare, Buddhist-majority Myanmar has suffered bouts of sectarian violence in recent years.
The unrest has been partially blamed on anti-Muslim rhetoric spread by a radical wing of Buddhist monks.
"The preaching event by U Wirathu is banned because of security reasons at this moment," a regional government official told AFP on the condition of anonymity.
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Director of the Ministry of Religious Affairs and Culture Aung San Win also told AFP the government was trying to restrict "writing that could incite tension over the assassination of NLD party legal advisor U Ko Ni".
Ko Ni was a rare voice for religious pluralism and his killing has sent shock waves through Myanmar's already hard-pressed Muslim community.
The 63-year-old also criticised the military's lingering grip on power over the new civilian government led by Aung San Suu Kyi, which has described his death as a political assassination.
His death comes amid soaring tensions between Buddhists and Muslims, which make up about five percent of Myanmar's population, after the army launched a deadly crackdown on the Muslim Rohingya minority in northern Rakhine.
But escapees in Bangladesh, where almost 70,000 have fled, claim the military is raping, torturing and killing Muslims in a campaign rights groups say could amount to crimes against humanity.
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