Statistics bureau chief Suhariyanto said the inflation pattern was unusual, as traditionally the inflation rate rises in the period that coincides with the start of the Ramadan fasting month.
Leading losses in the region, Indonesia's benchmark index closed 2.4% down, marking its worst day since April 16.
Telecommunications conglomerate Telekomunikasi Indonesia (Pereso) dropped almost 7% at close, while natural gas transportation and distribution company Perusahaan Gas Negara declined over 5%.
Meanwhile, risk sentiment in the session took a battering after US Secretary of State Mike Pompeo said on Sunday there was "a significant amount of evidence" that the new coronavirus emerged from a Chinese laboratory.
The accusation came after Donald Trump's threat late last week of retaliatory measures against China as punishment for the outbreak, once again sparking tariff fears that rattled markets through much of the last two years.
"Rekindling a dormant US-China trade war will likely make any economic improvement exponentially more difficult," Stephen Innes, chief market strategist at AxiCorp, said in a note.
Export-reliant Singapore, which is highly exposed to the US-China tariff tussle, saw its benchmark index settle 2.3% lower. Industrial conglomerate Sembcorp Industries' tumbled 5%, while Singapore Telecommunications' fell 3.5%.
The stock markets in the Philippines' and Malaysia both closed around 2.2% lower, following coronavirus-weakened economic data on Monday.
Philippine property developer SM Investments Corp ended 2.7% down, while Malaysian telecommunications conglomerate Axiata Group finished 3.8% down. The Thai stock market was closed on Monday for a national holiday.