Taiwan President Tsai Ing-wen has written to Prime Minister Lee Hsien Loong to thank Singapore for sending help to the quake-hit island, a move she said underscored friendly relations between the two sides.

The Singapore Armed Forces flew humanitarian supplies worth $135,000 to Taiwan on Friday (Feb 9), after the island's eastern coastal city of Hualien was hit by a magnitude 6.4 earthquake on Feb 6.

Fifteen people have been confirmed killed in the disaster, while some 280 were injured.

In a letter sent to PM Lee on Friday, Ms Tsai thanked Mr Lee and the people of Singapore for the aid rendered "in the shortest time possible", Taiwan's Presidential Office said on Saturday (Feb 10).

The aid, which helped to boost the rescue work and "warmed the hearts" of Taiwanese affected by the quake, symbolises the friendly relations between the two sides, the president was cited as saying.

Taiwan treasures its friendship with Singapore, she added, and hopes bilateral relations will continue to strengthen.

Correction note: This story has been edited for clarity.