SEOUL (Reuters) - South Korea's foreign exchange reserves increased slightly in July, central bank data showed on Wednesday, ending four straight months of decreases led partly by authorities' dollar-selling intervention to support the won.

The country's foreign exchange reserves, measured in U.S. dollars, increased in July by $0.33 billion to reach $438.61 billion at the end of the month, the Bank of Korea said in a statement.

It was the first monthly increase after a combined $23.49 decrease in last four months and only a second one since October 2021.

The BOK said the increase resulted from foreign asset investment returns and an increase in financial institutions' foreign currency deposits that offset a decrease in converted value of non-dollar assets.

The won weakened less than 0.1% against U.S. dollar in July, following a 4.7% slump in the previous month.

(Reporting by Jihoon Lee; Editing by Michael Perry)