Assets in U.S. exchange-traded funds rose $33.6 billion in September to reach a record $695 billion.

Overall ETF assets were up 5.1% in the month, driven by strong market performance of international equity funds and money flowing into fixed-income funds, State Street Global Advisors reported Thursday.

Assets increased in all ETF categories, with the international group gaining the most in dollar terms, up $12.6 billion to $162.6 billion in September, State Street said. Assets in fixed-income ETFs rose to $90 billion, up 6%.

This year through September, assets in international and fixed-income ETFs have risen 56% and 61%, respectively.

Global and commodity ETFs also experienced hefty percentage increases in assets in the month. Assets in global ETFs rose to $5.1 billion, up 9.3%, in September, according to State Street. Assets in global funds have risen nearly 34% this year through September.

Commodity ETF assets rose to $59.1 billion, up 8.3%, in the month, with SPDR Gold Shares (GLD) contributing $2 billion of the $4.5 billion increase. Assets in commodity ETFs have increased nearly 80% so far this year.

Leveraged and inverse ETFs, which have raised concerns among regulators due to their complexity, also gained assets in the month. Assets in these instruments - which seek to multiply or return the opposite of an index - were up more than $29.3 billion, or 1.9% in the month, State Street said. Assets in these funds have risen 35% this year through September despite the controversy surrounding them.

Barclays Global Investors (BGI), State Street Global Advisors and the Vanguard Group together account for about 84.3% of the U.S.-listed ETF market.

By Daisy Maxey, Dow Jones Newswires; 212-416-2237; daisy.maxey@dowjones.com