Singapore’s Transport Minister S. Iswaran facing 27 charges in a graft investigation, making it one of the rare corruption cases the country has seen in decades.

Iswaran, who was charged by the Corrupt Practices Investigation Bureau, vehemently denied the allegations in a resignation letter dated Tuesday.

In the letter published by the prime minister’s office on Thursday, Iswaran asserted, “I reject the charges and will now focus on clearing my name.”

Alongside his resignation, he pledged to return his salaries and allowances since the start of the investigations last July. Iswaran had been on a leave of absence but was still receiving monthly payments.

The CPIB accused Iswaran, arrested in July last year, of receiving kickbacks totaling S$384,340.98 ($286,181) from property tycoon Ong Beng Seng to advance Ong’s business interests.

The charge sheets revealed a series of alleged favors, including tickets to football matches, musicals, a flight on Ong’s private plane, and tickets to the Singapore Formula 1 Grand Prix. Iswaran, as an advisor to the Grand Prix’s steering committee, was linked to Ong, who owns the rights to the race.

The charges against Iswaran have shocked Singapore, known for its reputation of clean governance.

Iswaran, overseeing the tourism industry during the glitzy debut of the Formula One Grand Prix in the city-state, was a prominent figure in government.

His resignation came as a significant blow to the ruling People’s Action Party.

Singapore’s political circles have been shaken by a series of scandals, tarnishing the PAP’s reputation for combating corruption.

The last high-profile corruption probe involving a minister dates back to 1986 when National Development Minister Teh Cheang Wan faced investigation, leading to his tragic suicide before formal charges were filed.