HONG KONG — A brewing trade war between China and the United States sent markets reeling across Asia on Friday, following a sell-off on Wall Street overnight.

Investors drove stocks into red territory from Shanghai and Hong Kong to Tokyo and Seoul as they digested news that the Trump administration would impose stiff tariffs on Chinese goods. Markets fell further as Beijing announced retaliatory tariffs on more than 100 items, including American pork and wine.

By the close of trading on Friday, shares had fallen 3.4 percent in Shanghai and 4 percent in Shenzhen. In Tokyo, major exporters like Toyota and Sony helped to lead a 4.5 percent drop in the market. South Korean stocks fell 3.1 percent.

“This can turn ugly on a global scale very quickly,” Robert Carnell, chief economist for the Dutch financial services group ING Asia, wrote in a note to clients.

Europe looked poised for a similar sell-off, with futures flashing red for major markets.

Markets were following the lead of stocks in the United States, which fell for a second straight day on Thursday, as President Trump announced $60 billion worth of annual tariffs on Chinese imports.

After wobbling throughout the day, the Standard & Poor’s 500-stock index turned decisively lower in the last hour of trading, closing down by 2.5 percent. That put the index into negative territory for the year.

The trade measures against China were the latest demonstration of Mr. Trump’s “America First” agenda, and they were announced a day before tariffs on global steel and aluminum imports were expected to take effect.

The potential ripples of the trade actions have unsettled investors.

Tensions escalated on Friday as Beijing responded to Washington with its own tariffs and a warning to “avoid damage to the broader picture of Chinese-U.S. cooperation.” The Ministry of Commerce announced plans to slap tariffs on 128 products that would collectively be worth $3 billion in imports from the United States, including a 15 percent tariff on steel pipes, wine and fresh fruit, and a 25 percent tariff on pork.

The war of words spilled over into China’s state-controlled media, as the Global Times newspaper warned in an editorial that Chinese citizens would likely start campaigns to boycott American cars and other products.

Some American businesses in China also voiced concern. “Our members do not want to see a trade war,” said Kenneth Jarrett, the president of the American Chamber of Commerce in Shanghai. “The stakes are too high and there would be no winner,” Mr. Jarrett said.

But he added that American businesses in China wanted “fairer treatment and improved market access in China. The Chinese government has the ability to deliver against that reasonable expectation.”

In the United States, shares of large exporters, whose fortunes could be harmed by a trade war, were hit especially hard on Thursday and looked ready to bear the brunt of more selling on Friday. Shares of Boeing, one of the country’s largest exporters, and Caterpillar, which counts China as an important market, both fell by more than 5 percent.

Shares of large technology companies, which had already been reeling in anticipation of tougher government oversight, also took a hit. Facebook, which has been contending with a crisis over data privacy, slumped by more than 2 percent. Alphabet, Google’s parent company, dropped by more than 3.7 percent.

Amid the dip in stocks, money flowed to government bonds as investors sought safety, briefly driving yields on the benchmark 10-year Treasury note below 2.8 percent. Yields move in the opposite direction of bond prices. Commodities heavily geared toward global growth also fell. The price of West Texas intermediate crude oil, the American benchmark, slipped 1.2 percent. Copper, an important industrial metal, dropped 0.9 percent.

Thursday’s decline is the latest in a series of jolts to stock markets in the past two months.

After more than a year of calm, in which stock markets glided to one record high after another, a wave of volatility is suddenly cresting. There have been many causes of the turbulence this month and last. Investors initially were fearful that the economy was getting too strong, and that rising wages might cause inflation, which would push the Federal Reserve to hike interest rates faster than investors previously had expected. Those concerns have partly faded as recent economic data showed that inflation remained in check.

More recently, market anxiety has shifted toward worries about geopolitics.

A growing public backlash against technology companies has increased the chances that lawmakers and regulators in the United States and elsewhere will intensify their scrutiny of them. Shares of those companies have helped propel markets to record highs, and their recent declines have led markets lower.

Now, the prospect of a trade war between China and the United States, the two largest economies, has added to the gloomy sentiment. Among the concerns is that protectionism poses a risk to the health of the world economy. On Thursday, for example, the Bank of England warned that the erection of international trade barriers could have a “significant negative impact” on global growth.

Stock markets around the world have reflected the worries. A leading European index, the Stoxx 600, fell more than 1.5 percent on Thursday. In Germany, whose economy is dependent on exporting products all over the world, the DAX index dropped 1.7 percent.