Singapore Prime Minister Lee Hsien Loong has successfully undergone surgery for prostate cancer and is expected to make a full recovery, his office said.

On Sunday, Lee's office announced he would have an operation on Monday to remove his prostate gland and would take a week of medical leave, with Deputy Prime Minister Teo Chee Hean heading the government.

"The surgery went very smoothly, and he is expected to recover fully," Professor Christopher Cheng, the lead urologist at the Singapore General Hospital, said in a statement on Monday.

Lee, 63, was previously diagnosed with lymphoma in 1992 but the cancer went into remission after successful chemotherapy.

Cheng said there was no relationship between the previous lymphoma and the current prostate cancer.

Lee's illness raises questions about the need for a public succession plan should he step down in the future, as his ruling People's Action Party has not named a successor.

"Given that prostate cancer is not uncommon among people of a certain age and is, indeed, easily treated, the issue is not urgent," said Manu Bhaskaran, Singapore-based partner at Centennial Asia Advisors, a policy advisory group based in Washington, DC.

"However, more people could well focus on the issue now."

But the strength of political institutions and the durability of the national consensus was more important to
political stability, he said.

"On both these scores, Singapore does well," Bhaskaran said.

Singapore's two previous changes of prime minister since independence in 1965 involved well-flagged transitions to previously anointed successors.

Lee hinted in an interview with domestic media last month that his successor could be a member of his cabinet.

The next election must be held by January 2017, but media and internet blogs have speculated it could come as early as this year, after celebrations in August of Singapore's 50th anniversary of independence from Britain.

Source: Reuters