Sri Lanka President Gotabaya Rajapaksa emailed a letter of resignation to the speaker of the country's parliament late on Thursday, a source familiar with the matter said.
It was not immediately clear if the letter, sent shortly after Rajapaksa arrived in Singapore, would be accepted in email form, the source added.
(Reporting by Waruna Karunatilake in Colombo; Writing by Alasdair Pal; editing by John Stonestreet)