Sri Lankan President Gotabaya Rajapaksa submitted his resignation by email to parliamentary speaker Mahinda Yapa Abeywardenena on Friday, a statement from the speaker's office disclosed.
The speaker's office confirmed that Abeywardenena has received an email with Rajapaksa's resignation, but added that "we cannot accept such an email at face value."
Rajapaksa arrived in Singapore earlier on a flight from Maldives, having fled his nation in response to anti-government demonstrations.
"The legality of it must be determined. It has been sent to the appropriate authorities for verification," the office reported.
"Once we receive official confirmation and it has been legally verified, we plan to issue a statement about it on Friday," the message read.
In addition, Abeywardenena's office expects to get a hard copy of the letter, which would take longer to arrive because it will be mailed from Singapore.
The letter was emailed, according to a high-ranking government source, after Rajapaksa arrived in Singapore. Under the condition of anonymity, the insider divulged information that has not been made public by officials.
According to Singapore, Rajapaska was permitted to enter the country for a "private visit" but neither requested nor was granted refuge.
"It is verified that Mr. Rajapaksa has been granted private admission into Singapore. He has not requested asylum, and he has not been granted asylum.
In general, Singapore does not grant asylum claims, the statement from the Singapore Foreign Ministry said.
Rajapaksa vowed to resign over the weekend after irate protesters broke into his official mansion, swam in his pool, and demanded the end of the governing dynasty of his family.
Reporters were informed by a high-ranking security source in Colombo that he left the Maldivian capital Malé on a "Saudi flight."
Reporters believe that the source was referring to Saudia flight 788, which departed Malé at 11:30 a.m. Thursday at 7:17 p.m. local time, the flight landed in Singapore, according to the Changi Airport website.
Reporters have reached out to Saudia, the national airline of Saudi Arabia, but have not received a response.
Rajapaksa had been in Maldives for one day, having fled Sri Lanka in the early hours of Wednesday, the same day he announced his resignation.
However, the absence of a formal resignation letter prompted suspicions regarding the intentions of a self-exiled leader who nominated the prime minister as acting president after departing his island nation.