* ASEAN to meet on Saturday to discuss Myanmar
* Junta chief to attend - Nikkei Asia report
* Activists wear blue shirts to protest detentions
* Junta outlaws rival civilian government
Myanmar anti-coup activists launched protests on Wednesday calling for the release of detained prisoners, as junta chief General Min Aung Hlaing was reported to be planning to attend a regional summit to discuss the crisis in the country.
Saturday's summit of the Association of Southeast Asian Nations (ASEAN) would be its first since the coup in Myanmar on Feb. 1 and a test of how the traditionally consensual organisation will respond.
Junta spokesman Zaw Min Tun said the military commander would attend the meeting in Jakarta, Indonesia, the online service of the Japanese news magazine Nikkei Asia reported.
Reuters could not reach the spokesman for confirmation. The general's attendance at the summit has been condemned by critics of the military takeover both within Myanmar and abroad.
The Southeast Asian country has been in crisis since the military seized power from Aung San Suu Kyi's elected government, with almost daily protests despite a crackdown by the junta in which hundreds of people have been killed.
ASEAN has been trying to guide fellow member Myanmar out of the bloody turmoil triggered by the coup, but the 10-nation group's principles of consensus and non-interference have restricted its ability to overcome members' divergent views on how to respond to the army's killing of civilians.
Myanmar's military has shown little willingness to engage with its neighbours and no sign of wanting to talk to members of the government it ousted, accusing some of them of treason, which is punishable by death.
Malaysian Prime Minister Muhyiddin Yassin and Vietnam's Prime Minister Pham Minh Chinh will attend the summit, but Thai Prime Minister Prayuth Chan-ocha said he would be represented by his deputy, Don Pramudwinai, who is also foreign minister.
Other regional leaders are yet to confirm their plans.
The United Nations special envoy for Myanmar, Christine Schraner Burgener, will fly to Jakarta and hold meetings on the sidelines of the summit, three sources said.
She has communicated with Myanmar's military but the army has not allowed her to visit.
The Assistance Association for Political Prisoners (AAPP), an activist group, says 738 people have been killed by Myanmar's security forces since the coup and 3,300 people are in detention. Another 20 people have been sentenced to death and are in hiding.
On Wednesday, people shared photos on social media wearing blue shirts and holding up a hand with the name of an arrested person written on it.
The shirts are a tribute to pro-democracy activist Win Tin who was imprisoned by the military for 19 years and died on April 21, 2014. After his release, he pledged to wear a blue shirt until all political prisoners were freed.
"Please raise your voice and demand the release of all the people who are being unfairly detained under the junta government," protest leader Ei Thinzar Maung said on Facebook.
Last week, pro-democracy politicians, including ousted members of parliament, announced the formation of a National Unity Government (NUG) that nominally includes Suu Kyi, who has been in detention since the coup, as well as leaders of the protests and ethnic minorities.
Mynamar's home affairs ministry has declared the NUG unlawful, but the NUG says it is the legitimate authority in Myanmar and has requested international recognition and an invitation to the Jakarta meeting.
A grouping of ASEAN lawmakers also said the NUG should be invited.
"ASEAN cannot adequately discuss the situation in Myanmar without hearing from and speaking to the National Unity Government," ASEAN Parliamentarians for Human Rights said in a statement.
On the invitation to Senior General Min Aung Hlaing, it said: "ASEAN must make it abundantly clear that he is not there as a representative of the Myanmar people, who totally reject his barbaric junta."
Human Rights Watch said the 10-member bloc should immediately withdraw the invitation to the junta's leader.
"Min Aung Hlaing, who faces international sanctions for his role in military atrocities and the brutal crackdown on pro-democracy protesters, should not be welcomed at an intergovernmental gathering to address a crisis he created," said Brad Adams, Asia director at Human Rights Watch.
