JAKARTA (AFP) - Indonesia, South-east Asia's biggest economy and a key partner of Thailand in the regional Asean bloc, expressed serious concern after the Thai army declared martial law on Tuesday.

"We have been deeply concerned... following the developments in Thailand," Foreign Minister Marty Natalegawa told AFP.

"Indonesia has consistently called for respect of constitutional process and democratic principles in order to promote national reconciliation and unity, reflecting the wishes of the Thai people.

"It is our hope that this latest development will not detract from such principles and normalcy can quickly be restored." Indonesia and Thailand are both leading players in the Association of Southeast Asian Nations (Asean).

The Thai army made the declaration of martial law early on Tuesday on military-run television, stressing that the move "is not a coup" but that it wanted to restore order after months of deadly anti-government protests.