Hundreds of National League for Democracy party members, supporters and about a dozen foreign diplomats gathered at the NLD headquarters to commemorate Martyrs’ Day on Wednesday under the watchful eye of plainclothes police and other security officials.

July 19 commemorates nine fallen national heroes who were gunned down in 1947. They include General Aung San, father of detained opposition leader Aung San Suu Kyi.

An NLD anniversary statement called for the release of Suu Kyi, who has been under house arrest for most of the last 17 years, and other detained political leaders.

More than 30 former student leaders, including Min Ko Naing, attempted to visit Martyrs’ Mausoleum to pay tribute to the slain leaders, along with dozens of NLD supporters. But observers said security forces barred the mausoleum visitors because they were wearing Burmese traditional coats and T-shirts with images of Suu Kyi and her father.

The military government expanded the road block outside Suu Kyi’s house and increased security elsewhere in Rangoon. Last week the government’s newspapers accused the NLD and other dissidents of plotting with “terrorists” to disrupt the annual event.

Meanwhile, culture minister Maj-Gen Khin Aung Myint and national police chief Brig-Gen Khin Yi led the official ceremony on Wednesday morning. They laid wreaths at the Martyrs’ Mausoleum. Suu Kyi’s elder brother, Aung San Oo, represented his family.

Martyrs’ Day is a national holiday, but since 1990s the occasion has been gradually downgraded. Official media have abandoned an earlier tradition of carrying biographies of Aung San and his comrades.

“It’s a shame. It shows a lack of political maturity,” said veteran politician Amyotheryei Win Naing. “Even if they have an aversion to a daughter, we shouldn’t throw away her father’s biography.”