TOKYO -- Asian currencies are being dragged down by market concerns about overinvestment in AI and increasingly expensive oil, although central banks in some countries have helped their currencies buck the trend with defensive measures.

As hyperscalers vie to pour more money into artificial intelligence, investors are growing skeptical about the lack of a clear path toward the growth needed to recoup these costs. Meta Platforms' July-September earnings, released Wednesday, showed the Facebook owner's first-ever negative free cash flow since going public in 2012.

The Philadelphia semiconductor index, which covers major U.S. chip-related shares, was down 15% on Friday from the start of October.

Amid the U.S. stock fluctuations, the New Taiwan dollar slumped to the upper 32 range against the U.S. dollar at one point on Oct. 20 -- its weakest level in a year and a half.

Taiwan's semiconductor industry, led by Taiwan Semiconductor Manufacturing Co., has close business ties with American technology giants.

"The uncertainty that comes with the correction in U.S. stocks is spilling over to the local currency through a decline in Taiwanese stocks," Mizuho Bank senior market economist Takahiro Hori said.

The rise in crude oil prices is also spurring currency-selling across Asia. Many countries rely on imports to meet most of their energy needs, meaning that high crude prices add inflationary pressure. The Philippine peso touched the 64 range against the dollar Monday, its weakest level to date.

The turmoil in the Middle East is deepening as Iran-backed Houthis in Yemen ramp up attacks on Saudi Arabia. With reports indicating the U.S. has made plans to resume attacking Iran after next week's midterm elections, oil prices look unlikely to settle down anytime soon.

A weak currency erodes a country's economic strength by hurting terms of trade, which can drive a currency sell-off in vicious circle. The central banks of South Korea and India have moved to shore up their countries' currencies.

The won on Monday touched 1,319 to the U.S. dollar, its strongest in roughly two years, even as the benchmark KOSPI index -- which is weighted heavily toward such semiconductor companies as Samsung Electronics and SK Hynix -- is down around 40% from its June peak.

The Bank of Korea decided last Thursday to leave its policy interest rate unchanged at 3% following hikes in July and August but left the door open to further increases, signaling a strong stance against inflation.

Real demand for memory chips has also played a role. South Korea logged a record-high trade surplus of about $50 billion in September.

India, meanwhile, saw the rupee soften to the upper 96 range against the dollar early this month -- its weakest in four and a half months -- before recovering to the 94 range.

The rebound owes in large part to the Reserve Bank of India's efforts to defend the currency, which include setting up a mechanism to supply dollars to state-run oil companies and restricting currency derivative transactions to curb speculation.

Concerns over AI investment and high oil prices appear likely to persist, keeping emerging Asian economies vulnerable to currency-selling. Central banks' capacity for policy responses could play a key role in how these currencies fare.

The Philippine central bank raised interest rates on Thursday, but this failed to check the peso's decline with inflation running above 7%. "They've been cautious about raising rates so far, so monetary policy has been behind the curve on addressing inflation," said Toru Nishihama, a chief economist at the Daiichi Life Research Institute.

As for India, "the rupee is bought again whenever the central bank comes out with currency defense measures, but such buying lacks sustainability," said Shinya Harui, senior foreign exchange analyst at Nomura Securities.