President Tony Tan Keng Yam and Prime Minister Lee Hsien Loong wrote to Mr Rodrigo Duterte to congratulate him on winning the Philippine presidential election.

Dr Tan, in his letter yesterday, described both countries as "old friends with strong ties" and which cooperate closely in Asean and internationally to promote peace, stability and prosperity.

Recalling his state visit there in April 2014, Dr Tan said he and his wife were impressed by the economic progress, and the resilience of the residents of Tacloban in the aftermath of the devastation brought by Typhoon Yolanda.

Expressing confidence that Mr Duterte would lead the economy to greater heights, Dr Tan wished the President-elect success and invited him to visit Singapore at the earliest opportunity.

PM Lee, in his letter yesterday, said the strong mandate Mr Duterte received "reflects the trust that your fellow Filipinos have in your leadership and vision for the Philippines".

Singapore and the Philippines share close ties in many areas, including trade and investment, culture and people-to-people exchanges, Mr Lee said.

He noted that relations will reach a milestone in 2019 with the celebration of 50 years of diplomatic ties.

Both countries are Asean founding members and "we cooperate closely to promote regional peace and prosperity", Mr Lee said.

Singapore looked forward to the Philippines' chairmanship of Asean next year - which is also Asean's 50th anniversary.

"I am confident that we will be able to foster closer Asean integration amid a complex and fast-changing global landscape," Mr Lee said, adding that he looks forward to working with Mr Duterte.