Southeast Asian nations said on Wednesday they are "deeply concerned" about the violence ravaging Myanmar, and condemned a recent attack on a convoy of diplomats delivering humanitarian aid in the country.

Turmoil in junta-ruled Myanmar has dominated talks at this week's Association of Southeast Asian Nations (Asean) summit in Indonesia, as the regional bloc faces criticism for its perceived inaction.

Asean has led diplomatic attempts to resolve the festering crisis, but its efforts so far have failed to stem the bloodshed unleashed by a military coup in 2021.

"We were deeply concerned with ongoing violence in Myanmar and urged the immediate cessation of all forms of violence and the use of force to create a conducive environment for the safe and timely delivery of humanitarian assistance and inclusive national dialogues," Asean leaders said in a statement.

The junta has ignored international criticism and refused to engage with its opponents, which include ousted lawmakers, anti-coup "People's Defence Forces" and armed ethnic minority groups.

An air strike on a village in a rebel stronghold last month that reportedly killed about 170 people sparked global condemnation and worsened the junta's isolation.

Pressure on the regional bloc increased on Sunday after a convoy of vehicles carrying diplomats and officials coordinating Asean humanitarian relief in Myanmar came under fire.

Singapore and Indonesia said earlier that staff from their embassies in Myanmar were in the vehicles that came under fire in eastern Shan State but were unharmed.

"We condemned the attack and underlined that the perpetrators must be held accountable," Asean leaders said in their statement.

Addressing the summit on Wednesday, Indonesian President Joko Widodo said he was "confident" the 10-member bloc could deal with growing global challenges if its members were united.

"With unity, Asean will be able to play a central role in bringing peace and growth," Widodo said through a translator as he opened the leaders' session of the summit. (AFP)