In Onitsha, the economic hub of Anambra state on the banks of the River Niger, most markets were closed and the streets were largely empty of people and traffic.
Separatist sentiment persists in the region, which is dominated by the Igbo people, and the main pro-Biafran independence group has called on supporters to stay at home.
"No work today, we are Biafran, we are not Nigerians," said Ebere Ichukwu Eli, one of the few people to venture outside, where there was a visible security presence.
A woman who gave her name only as Justine, said: "The market is closed today. I'm just going home to stay with my children.
"We want our one Biafra. It's our land. That's why we all sit at home today."
The closures were either to commemorate the anniversary in support or because of fears of violence, local people said.
Nigerian police last week denounced "planned protests and order of market closures" and warned it would "deal decisively" with any breach of the peace or unlawful protest.
Since August 2015, more than 150 people have been killed in pro-Biafra protests, said Amnesty's Nigeria director Osai Ojigho. Nigeria's government denies the claim.
"We urge the Nigerian security agencies to conduct themselves in a manner that will ensure public order without resorting to force," he added.
Amnesty said the security forces had arrested more than 100 members of pro-Biafran separatist groups in the run-up to Tuesday's anniversary.
Calls for independence never disappeared even after the 30-month civil war, which left more than one million dead, most of them Igbos, mainly from starvation and disease.
Support for secession has increased since the arrest in late 2015 of Nnamdi Kanu, the leader of the pro-independence Indigenous People of Biafra (IPOB) movement.
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