It was a day of firm handshakes and warm words as political leaders and defence chiefs met ahead of the Shangri-La Dialogue security conference.

Besides Indian Prime Minister Narendra Modi, United States Defence Secretary James Mattis and newly-minted Malaysian Defence Minister Mohamad Sabu also called on Prime Minister Lee Hsien Loong at the Istana on Friday (June 1).

PM Lee congratulated Mr Mohamad on his appointment and talked about the close relations and extensive cooperation between the two countries. Mr Mohamad is on his first official visit here after his Pakatan Harapan coalition swept into power on May 9.

Mr Mattis and PM Lee reaffirmed the excellent and longstanding bilateral relations between Singapore and the US, and discussed regional security developments, including the importance of the US' continued engagement of the Asia-Pacific.

Mr Mattis had earlier met his Singapore counterpart, Dr Ng Eng Hen. Over breakfast, he stressed the continued commitment from the US to engaging countries in the region and the important role that Asean has to play as part of the US' vision for a "free and open Indo-Pacific".

The two men also talked about the situation in the Korean peninsula and the terrorism threat in South-east Asia, said a Defence Ministry statement.

Mr Mattis will speak at the Shangri-La Dialogue on Saturday (June 2) morning, where he is expected to explain the US' regional role.

On Friday, Mr Mattis and Dr Ng co-chaired an informal meeting with South-east Asian defence ministers who have gathered in town for the conference.

They discussed the growing terror threat in the region, especially the dangers of returning fighters. They welcomed Singapore's push as this year's Asean chair to beef up counter-terrorism cooperation among the militaries, including sharing intelligence.

Dr Ng also met Lieutenant-General He Lei, vice-president of the People's Liberation Army (PLA) Academy of Military Science, on Friday.

Both men reaffirmed their strong bilateral defence relationship. Dr Ng accepted Lt-Gen He's invitation to this year's Xiangshan Forum, a rival security conference to Shangri-La Dialogue, in September.

Both men welcomed the inaugural Asean-China Maritime Exercise later this year, which would bring Asean member states and Chinese navies closer.

The Singapore Armed Forces and the PLA interact regularly through port calls, bilateral exercises and exchanges of visits.

Dr Ng on Friday also met his counterparts from South Korea, Canada and New Zealand.