The Swiss-run International Committee of the Red Cross has said that it is "deeply worried" about the fate of those arrested in Myanmar.
It said it was seeking access to thousands of people who were detained during the recent crackdown in the country, but that the authorities had not yet agreed to talks.
In an interview posted on its website, Pierre Krähenbühl, the organisation's director of operations, said efforts would continue to restore a "meaningful" dialogue with the authorities concerning the current situation and violations of humanitarian law previously raised by the ICRC.
At least ten people were killed and many were arrested during last month's suppression of pro-democracy protests led by Buddhist monks in Myanmar.
Myanmar police are still reported to be raiding homes and arresting activists.
"The ICRC is deeply worried about the fate of thousands of people who have reportedly been arrested in connection with the recent events in Myanmar," Krähenbühl said in comments dated October 15.
The Geneva-based agency wants access to the recently detained people to "assess their conditions of treatment and detention" and to help them contact loved ones.
Krähenbühl said dozens of worried families had contacted the ICRC for help locating relatives that have been reportedly detained or are missing.
He said that the organisation's efforts to talk to the government had so far not borne any fruit. "We regret that our efforts have not yet produced any tangible results but we remain determined to pursue them," said Krähenbühl.
On June 29 the ICRC issued a rare public statement about the situation in Myanmar.
It accused the junta of serious violations of international humanitarian law against civilians and prisoners and urging the government to take action.
The ICRC said at the time that it had been unable to visit any of Myanmar's 1,100 political prisoners since late 2005.
The organisation continues its physical rehabilitation services for amputees and mine victims in Myanmar, and facilitates some family visits to detention centres, spokeswoman Carla Haddad told Reuters.
On Tuesday Japan, Myanmar's largest aid donor, cancelled a multimillion dollar grant to Myanmar to protest against the crackdown, as a United Nations envoy pressed Asian nations to take the lead in resolving the crisis.
Japan said it would suspend some assistance in response to the death of a Japanese video journalist during the violence.
On Monday, the European Union upped sanctions on Burma and the United States urged "consequential" action against its leaders.
The Swiss ambassador to the UN in Geneva, Blaise Godet, earlier this month demanded the immediate release of peaceful protestors and political prisoners in Myanmar.
He was addressing the UN Human Rights Council in Geneva, which has condemned Myanmar's "violent repression" of protests.
swissinfo with agencies
Myanmar, formerly Burma, has been under military rule since 1962.
A massive hike in fuel prices last month sparked almost two weeks of sustained popular protest which were halted when police and soldiers moved against protesters late last week.
The UN says the junta has more than 1,100 political prisoners. An unknown number of protestors have been detained.
Nobel peace laureate and opposition leader Aung San Suu Kyi has been under house arrest for 11 of the past 17 years.
ICRC staff have not visited her since September 2003.
Switzerland and Myanmar
The Swiss foreign ministry is advising citizens to stop non-urgent travel to Myanmar. It says if travel is unavoidable, people should inform themselves via the media and follow local authorities' instructions.
The ministry says Swiss citizens should stay away from any street protests.
There are currently about 50 Swiss residents in Myanmar and the foreign ministry has said it is in contact with the Swiss community.