The military regime has kept the Nobel Laureate in detention for 13 of the past 19 years, and she is now on trial at Yangon's notorious Insein Prison over a bizarre incident in which an American man swam to her home.
Key aide Nyan Win said he had gone to the prison to take her a spicy rice dish, chocolate birthday cake and flowers which she planned to share with guards. He handed over the gifts but was not allowed to see her, he said.
"She ordered the food so that she could donate it to those around her in prison, and there are no other prisoners near her. She will hold a small ceremony there," said Nyan Win, the spokesman for her National League for Democracy (NLD).
Around 300 supporters gathered at the NLD's headquarters in Yangon and offered food to Buddhist monks at dawn, before releasing 64 doves and balloons into the air in a symbol of freedom before sharing a birthday cake.
Security was tight for the celebrations with plainclothes police videotaping people entering the building and five police trucks patrolling nearby, witnesses said.
The ruling generals refused to recognise the NLD's landslide victory in 1990 elections, and critics say the latest charges against her are trumped up to keep her behind bars for polls promised by the generals in 2010.
Aung San Suu Kyi's trial, which could see her jailed for up to five more years, has provoked international outrage.
Myanmar's top court will next Wednesday hear an appeal by her lawyers to reinstate two witnesses who were barred from testifying, a Myanmar official and Nyan Win said.
"Both the defence and prosecution will have to give their arguments. I will tell Daw Aung San Suu Kyi about it when I meet her on Monday," Nyan Win said.
Events to mark her birthday were scheduled in more than 15 cities around the world, ranging from evening vigils in Ireland and Australia and a party by Myanmar refugees living on the border with Thailand.
In London Aung San Suu Kyi's brother-in-law Anthony Aris offered a symbolic gift of flowers for her at a protest marking her birthday at the country's embassy.
"I am anxious. The family does not normally speak to the media, but these are exceptional circumstances," he said.
Police in Malaysia broke up a rally of about 40 activists, after around 200 people had demonstrated there earlier, chanting "Free Aung San Suu Kyi".
A similar number of Myanmar refugees and activists gathered in Tokyo to demand her release.
European Union leaders threatened Friday to slap new sanctions on the Myanmar regime unless it released Aung San Suu Kyi.
"The European Council calls for the immediate unconditional release of Aung San Suu Kyi, who has tirelessly defended the universal values of freedom and democracy," they said in a statement released after a two-day EU summit in Brussels.
McCartney, John Lennon's widow Yoko Ono and author Salman Rushdie on Friday became the latest celebrities to add special statements of 64 words or less to the website "64 for Suu."
"Aung San Suu Kyi is an inspiration to her country and the rest of the world," said McCartney's message, while Ono's read simply: ""FREE Daw Aung San Suu Kyi NOW!"
Britain's Brown earlier posted a video on the site, while Clooney, Roberts, footballer David Beckham and rocker Bono signed a letter saying: "Now is the time for the international community to speak with one voice: Free Aung San Suu Kyi."
A global petition was delivered on Monday to UN Secretary General Ban Ki-moon, signed by more than 670,000 people from 220 countries, calling for the release of all of Myanmar's political prisoners, especially Aung San Suu Kyi.
The US State Department, in a birthday message, urged the junta to free Aung San Suu Kyi "immediately", while Australia voiced "grave concern" over her treatment.
Ban is set to travel to Myanmar in early July after a visit to Tokyo, Japan's Kyodo news agency reported Friday, citing unnamed UN diplomatic sources. There was no immediate confirmation.
----------------------------------------------------------------------------------------------------------------------