Countries on three continents reported their first cases of the coronavirus on Friday as the world prepared for a pandemic and investors dumped equities.
The Thai benchmark was the worst hit in the region, shedding 3.9%, with heavyweights PTT PCL sliding 6.6% and Airports of Thailand down 4.8%.
Thailand's central bank said a prolonged outbreak may see economic growth of less than 1% in 2020. Last year, the economy grew 2.4%, which was its slowest rate in five years.
Stock markets in Singapore and the Philippines recorded their worst weeks since 2011, down 3.2% and 2.6%, respectively.
In Singapore, banking majors DBS Group Holdings fell 2.9% and Oversea-Chinese Banking Corporation 2.8%.
Malaysian stocks posted their worst weekly drop since 2015, further pressured by days of political turmoil after the surprise resignation of the prime minister.
The royal palace rejected on Friday Mahathir Mohamad's plan for a vote to choose a new prime minister.
The Bank Negara Malaysia is also expected to cut its benchmark interest rate at a policy review on Tuesday, a Reuters poll showed.
Indonesian shares posted their worst monthly fall since 2013, while the rupiah marked its steepest decline in more than eight years, prompting the central bank to intervene in the spot market.
However, shares recovered from sharp losses earlier in the session to close 1.5% lower.
Siantar Top TBK slumped 20%, while Mega Perintis tumbled to a record low.
(This story adds dropped article in lede.)
By Pranav A K