SINGAPORE, Oct. 22 — Renewed concerns about the health of the American economy sent Asian stocks sharply lower today, and European stocks also registered declines in early trading.

Following a dramatic decline by stock prices in the United States on Friday — the 20th anniversary of the 1987 “Black Monday” stock market crash — investors in Asia sold off stocks on worries that the United States mortgage crisis would crimp demand among American consumers for Asia’s exports.

Hong Kong’s benchmark index of share prices fell by almost 3.3 percent, while in Japan the benchmark Nikkei 225 Stock Average dropped by more than 2.2 percent. South Korean stocks fell by 3.25 percent. Asia’s smaller markets were also hard hit: stocks in the Philippines slid by roughly 4 percent.

In Europe during early trading, London’s FTSE 100 was down 88 points, or 1.4 percent, but was trading off its lows. The German DAX stock market index was down 1.3 percent, and the Paris market had fallen by around 1.8 percent.