SINGAPORE - Singapore Prime Minister Lee Hsien Loong has ordered an investigation into the circumstances around the rental of state-owned homes in an exclusive location to two cabinet ministers following questions from the opposition.

The matter has prompted comment in the wealthy city-state, which has long prided itself on a government free from corruption, with the annual salaries of many cabinet ministers exceeding S$1 million ($755,000) to discourage graft.

Lee said the review by a senior minister, whose results will be made public before lawmakers take up the issue in July, would establish whether "proper process" was followed in the rental of the colonial-era bungalows and if there was wrongdoing.

"This must be done to ensure that this government maintains the highest standards of integrity," Lee said in a statement.

This month, opposition politician Kenneth Jeyaretnam questioned how the law and home affairs minister, K Shanmugam, and the foreign minister, Vivian Balakrishnan, could afford the market rate for such "pricey" properties.

Shanmugam said accusations of impropriety were "outrageous" and he had nothing to hide. Balakrishnan said he was "very glad" a review was taking place.

Social media posts in Singapore mocked the ministers or expressed outrage over the size of the properties, while others questioned why the government needed time until July to explain the issue.

The expression of disapproval comes as many in Singapore battle rising living costs, amid high inflation and rising prices of homes and cars.

Eight in 10 of Singapore's 3.6 million citizens live in public housing and just a third of households own cars.

Lawmakers, including three members of the ruling party and the leader of the opposition, have submitted parliamentary questions on whether the ministers acted on privileged information to secure the leases.

The Singapore Land Authority has said the ministers leased bungalows that had been vacant for years and had made bids that were higher than the rent guidance, a price that had not been disclosed to them.

Government graft scandals are rare in Singapore.

A minister was investigated in 1987 but died before the inquiry concluded.

Lee and his father - founding prime minister Lee Kuan Yew - both addressed parliament in 1996 to answer accusations, investigated at the time by the prime minister, that the family had bought prime real estate at a discount.

The investigation concluded there was nothing improper about the Lee's property purchases.

($1=1.3245 Singapore dollars)