Prime Minister Fumio Kishida spoke by phone with his Thai counterpart Prayut Chan-ocha on Monday, voicing his desire to boost cooperation to realize a free and open Indo-Pacific region.

Prayut congratulated Kishida on taking office and expressed hope for stronger bilateral relations during the roughly 30-minute call, according to Japan's Foreign Ministry.

The two discussed the situation in Myanmar, which has been under military control since a coup in February, with Kishida pledging Japan's support for the Association of Southeast Asian Nations' mediation efforts.

Kishida also held 25-minute phone talks with his Singaporean counterpart Lee Hsien Loong, expressing a desire to step up bilateral cooperation in areas such as the environment and digital technologies, as well as the realm of security, the ministry said.

In the conversations with both leaders, Kishida voiced "strong opposition to unilateral attempts to change the status quo in the East and South China seas," criticizing Beijing's growing assertiveness without calling it out by name.

Japan views Southeast Asia as key for achieving its goal of a free and open Indo-Pacific region. Many countries there have strong economic ties with Beijing but are troubled by its expansive territorial claims.

Kishida is set to hold an in-person meeting with his Vietnamese counterpart Pham Minh Chinh in Tokyo on Wednesday, the first time he is hosting a foreign leader since taking office in early October.