Kyaw Ko Ko, leader of the All Burma Federation of Students Union, said 23 people were arrested in the crackdown, which began Friday night. His group had organized the commemoration.
On July, 7, 1962, students in Rangoon, the former name of Yangon, Burma's biggest city, staged a protest against the military regime of Gen. Ne Win, which had taken power four months earlier. Their protest was suppressed by force, and on July 8, the army blew up the student union building at Rangoon University. It is believed that dozens of students were killed in the crackdown.
"The authorities picked us up to prevent us from commemorating the July 7 event. The authorities are overly anxious and these [arrests] should not happen anymore when the country is on the road to democratic reforms," said Sithu Maung, 25, a student activist who was one of those detained.
He said the authorities explained their concerns, but the student group insisted its intention was not to create unrest but to remember the fallen heroes and let a new generation know the history of the student movement.
Ne Win's 1962 coup was the beginning of almost five decades of repressive military rule.
Current President Thein Sein, a former general, came to power with military backing after a 2010 general election. He has initiated reforms, including reconciliation with Aung San Suu Kyi, the leader of the country's pro-democracy movement, that are intended to boost economic development and have been well received by the international community.
"Even when the president has repeatedly said his government is making real reforms, it is very disappointing that there are some in the government who still cannot abandon their old habits," said Ko Ko Gyi, a leader of a failed 1988 democracy uprising who has spent many years in prison.
Student organization goes ahead with demonstration
Those detained included several activists who were freed from prison in January under an amnesty for political prisoners, Kyaw Ko Ko said. The amnesty was part of the liberalization policies initiated by Thein Sein's government to promote political reconciliation.
The authorities had warned the students' union not to carry out Saturday's commemoration, and the use of a hall where the event was supposed to held in Yangon was not allowed after its owner came under pressure, the activists said.
A group organized by Ko Ko Gyi and his colleagues, the 88 Generation Students, let the event be held at their office instead. Some 300 people gathered there, where they heard Min Ko Naing, a colleague of Ko Ko Gyi, praise the courage of the new generation of student activists who organized Saturday's commemoration.
Maung Maung Lwin, a freed activist in Mandalay contacted by phone, confirmed that all the detainees had been released by Saturday night.
"We were not mistreated but we didn't have a good night's sleep," he said.
Those detained included four activists from Yangon, four from Mandalay, four from Shwebo, seven from Myingyan, three from Lashio and one from Sagaing, according to Kyaw Ko Ko.