LONDON  In China and Taiwan, regulators are imposing fresh restrictions on stock market investments by foreigners. In Brazil, officials have twice raised taxes on foreign investors. Even in South Korea, host to this week’s Group of 20 meeting, pressure is building on the government to take similar steps.

As the leaders of the 20 major economic powers gather in Seoul, an increasing number of them have either imposed curbs or are in the process of doing so to slow the torrent of hot money into their markets.

Over the years, foreign capital flowing into emerging markets has played a crucial role in helping finance roads in India, factories in China and buyers of luxury cars in Brazil.

But as the sums have compounded and led to more market volatility, fast-growing countries have begun to worry that short-term investment will push up the value of their currencies, make their goods less competitive in the global market, and lead to asset bubbles that will be painful to deflate.