This prompted domestic investors to cash in gains.
Johannesburg-based NewPlat ETF, which tracks the rand-denominated platinum price, climbed more than 12 per cent from the start of the year to its late January high as the South African unit hit five-year lows against the dollar.
A move by the US Federal Reserve to reduce its monetary stimulus programme has led to concerns about economic growth and triggered an exodus from emerging markets.
More than 12 billion US dollar left emerging market stock funds in January alone, while on currency markets the rand was swept sharply lower along with the Russian rouble, Argentine peso, Turkish lira and others.
Rand-denominated platinum surged to 16,178 rand an ounce in late January and is now up nearly 8 per cent on the year, while dollar-priced spot platinum is up just 1.4 per cent.
Last week NewPlat ETF's holdings fell by 16,019 ounces to 885,206 ounces, its largest one-week drop since its launch last April, Reuters data showed. The fund's investors are largely South African pension and other funds, analysts say.
"The key thing that has changed in the last couple of weeks is that the rand has blown out against the U.S. dollar," Justin Froneman, an analyst at SBG Securities, said. "The rand platinum price has gone up, and there was quite a lot of profit sitting on the table.
"You will find there will be some people normalising their portfolio and taking some profit."
Last week's withdrawals have brought NewPlat ETF's total outflow since the start of 2014 to just over 24,000 ounces.
While the drop amounts to just 2.7 per cent of the total, it nevertheless marks a turnaround for a fund that attracted extremely strong inflows for most of 2013.
The fund has averaged weekly outflows of 4,061 ounces this year, compared with average inflows of 23,105 oz a week in 2013.
Precious metals-backed exchange-traded funds issue securities backed by physical metal, giving buyers exposure to the underlying price without taking delivery of the physical asset. They proved a popular way to invest in the sector after the financial crisis.
Platinum's heavy reliance on supply from South Africa, which produces three quarters of world supply, had made it a popular pick among precious metals in recent years as a wave of labour unrest hit mining companies there.
The NewPlat fund attracted a surge of interest after its launch last April as investors sought to benefit from an expected rise in platinum prices while avoiding exposure to the platinum producers, which have been dogged by rising costs and shrinking margins.
Within four months of its launch, the fund had become the largest of its type in volume terms.
But the expected price gains in dollar terms have not come through due to persistent weakness in demand, particularly within the European car sector which uses the metal in catalytic converters; plentiful availability of above-ground stocks; and weakness in gold, the bellwether precious metal.
Average spot platinum prices fell 4 per cent last year, against expectations for a 10 per cent rise, in a poll conducted by Reuters at the start of the year.
Some investors may have been disappointed by the metal market's lack of reaction to threats to South African supply last year, analysts said, and are now taking advantage of the currency-related price spike to take profits.
"People may be getting concerned that platinum prices in US dollars haven't been reacting much to the strike action and therefore taking some profits, particularly the earlier investors in the ETF, since in rand terms the metal has performed well," Investec analyst Marc Elliott said.
Some South African equities may also now appear to be a more attractive buy, he said.
"A lot of that ETF demand was people pulling out of the equities and going into the metal, so that may now be flowing back the other way," he said.