The Hong Kong dollar hit a three-week low on Friday afternoon after a rally in the US dollar against the yen sparked short covering on the greenback.
The local currency weakened to 7.7556 to the US dollar, at one point touching the lowest level since April 26, before trading back to 7.7551/53, down from Thursday's close of 7.7538/39.
"The Hong Kong dollar weakened, driven by some short-covering positions on the US dollar against Asian currencies in the wake of the greenback rising above 111 against the yen," said a dealer at a European bank.
The US dollar rose to a 10-day high against the yen on Friday on signs the Bank of Japan would not rush to raise the country's near-zero interest rates.
But some dealers said the downside of the Hong Kong dollar was capped by some foreign fund inflows for initial public offerings.
One trader expected the Hong Kong dollar to move in a range between 7.7540 and 7.7560 in the near term.