TAIPEI - Two high-level officials in President Tsai Ing-wen's administration are stepping down, just five months after she was sworn into office.

Presidential Office Secretary-General Lin Bih-jaw and National Security Bureau Director-General Yang Kuo-chiang announced on Thursday (Oct 19) that they have quit, the first high-level resignations from Ms Tsai's government.

The surprise departures are a blow to Ms Tsai, who is grappling with growing frustration among voters and lawmakers, sparked by controversial proposed labour policies on public holidays and workdays and unpopular pension reforms.

Presidential Office spokesman Alex Huang said on Thursday that Mr Lin, 67, is stepping aside because he felt that "his mission is complete" and the new government is "operating smoothly...allowing Ms Tsai to appoint another person to oversee the government's next phase (of development)."

Mr Huang said Ms Tsai "respects her old friend's wishes to retire to focus on his writing and thanks him for his hard work and assistance".

Mr Lin, who has previously served as vice-president of National Chengchi University and deputy secretary-general of the National Security Council, holds one of the most important jobs in Ms Tsai's administration as he is seen as one of her most trusted aides and is in charge of coordinating her agenda.

Mr Lin's deputy, Jason Liu, will be the acting secretary-general until a replacement is appointed.

National security czar Yang, 66, who was appointed in July last year had asked to step down on multiple occasions, said Mr Huang. He will be replaced by former air force commander Peng Sheng-chu Yang, 66.