In a rare public comment, the state-run New Light of Myanmar newspaper said the activists held on Tuesday were arrested for "undermining stability and security of the nation".
"Their agitation to cause civil unrest was aimed at undermining peace and security of the state"
New Light of Myanmar newspaper
No details were given of the alleged offences but those detained could face up to 20 years in prison.
"Their agitation to cause civil unrest was aimed at undermining peace and security of the state and disrupting the ongoing National Convention," the newspaper said.
The convention is currently drafting the country's constitution as part of what the military government says is a seven-point roadmap to restoring democracy in Myanmar.
Critics have dismissed the process as a sham.
Security in Yangon and Mandalay, the country's second largest city, has been tightened.
"People are facing a lot of difficulties and they want to do something, but they are afraid of being beaten to death or arrested"
Ko Bo Kyi, Assistance Association for Political Prisoners
Among those arrested are prominent former student leaders, all from the 88 Generation Students movement - a group which was at the forefront of the 1988 pro-democracy uprising.
Most were reportedly tortured and given lengthy jail terms after the uprising was suppressed by the military.
In a recorded statement released to Al Jazeera, another of 88 Generation leaders, Htay Kywe, who is now in hiding from the authorities, gave an acount of the recent arrest of his friends.
"Last night the military intelligence and government intelligence seized their house and sacked their house for no detailed reason," he said.
"They seized some papers and some material from that house and also many mobile phones were seized."
|In some cases the price of food has more than|
doubled as a result of the fuel hike [EPA]
On Sunday activists and former student leaders led more than 400 people in a silent march through Yangon, Myanmar's biggest city, after the government arbitrarily increased fuel prices by 100 per cent.
Following the price hike, the overall cost of essential goods and services has skyrocketed, and in some cases prices have more than doubled, activists say.
Ko Bo Kyi, the joint secretary of the Assistance Association for Political Prisoners based in Thailand, said at least nine of the detained activists were taken from their homes late on Tuesday.
"From what we know, they are being held at the Kyaik Ka San detention center outside Yangon," he told Al Jazeera. "We don't have all their names but I expect more to be arrested."
He said some activists have gone into hiding but the rest will continue their activities, including trying to organise a second silent march.
Ko Bo Kyi said security was very tight in Yangon.
"The situation is very bad here. I'm really worried that some activists might be beaten or detained," he said.
"People are facing a lot of difficulties and they want to do something, but they are afraid of being beaten to death or arrested."
He added, "Now people have to use half of their income for bus fares and students are badly affected because many of the universities are located outside of town."
According to US-based activist group, Myanmar authorities had also arrested a number of students.
The US Campaign for Burma, based in Washington, said five university students and three members of another activist group were arrested in separate sweeps.
Reports in government newspapers made no mention of these arrests.
The US group said three members of the Myanmar Development Committee, which had called for a nationwide protest against the fuel price hike, were also arrested along with the five students.
The Myanmar Development Committee has vowed to go ahead with the protests on Wednesday despite the arrests.
Pro-democracy groups in Myanmar have also appealed for support and urgent action from civil society organisations based on the Thai border and the international community.