The outflows in August comprised half of the quarterly total, at £1.6bn, with investors withdrawing capital from all equity market sectors except North America, which saw inflows of £70m.
UK equities accounted for £697m of the outflows in August.
But with doubts about the role of bonds as a diversifier in the current market conditions, investors also fled fixed income mandates, with £968m pulled from bond funds.
Laura Suter, personal finance analyst at investment platform AJ Bell, said: “Investors’ flutter with bond markets in July appeared short lived, with almost £1bn pulled from bond funds in August, following the more than £2bn of inflows we saw the previous month.
"It would seem investor worries about the lack of a clear direction from the Bank of England on interest rates, as well as changing monetary policy in Europe and the US and the soaring levels of negative interest on bonds have caused them to cool on fixed income."
Luca Paolini, chief strategist at Pictet Asset Management, said: “Corporate profits are barely growing. Almost £12trn of debt trades at yields below zero. And trade disputes are rumbling on.
"There is not much for investors to be enthusiastic about. Not in the near term at least.
"Economic conditions will likely remain sluggish over the next few months. Thus, we remain underweight bonds and equities and overweight safe haven assets.
"Trade is the economy's biggest problem. Although consumer demand is holding up, export orders are shrinking as a result of tariff hikes and other protectionist measures.”
But he said within equity markets he regards the US as expensive and is relatively keen on the UK and European markets.
He said Brexit has made UK-listed shares “the cheapest in the world”, while European consumers continue to spend, which he believes will help the returns from those equity markets.
Job Curtis, who runs the £1.7bn City of London investment trust, which invests in UK shares, said he has reduced the level of debt in the trust because UK stocks have risen in value this year, making them a less attractive investment.
Simon Edelsten, who runs the Artemis Global Select fund and the Mid Wynd investment trust, wrote in a note to unit holders: “Continued trade tensions – between China and the US, the UK and the EU and, potentially, the US and the EU – ensured August was a turbulent month.
"These tensions came at a time of slowing growth, especially in major European economies such as Germany and Italy, whose long stagnation continues.