Japan's top three banks on Thursday posted lower quarterly profits as the impact of last year's stock market surge faded.

Mitsubishi UFJ, the country's biggest lender, saw its net profit slip about six percent to 240.5 billion yen ($2.4 billion) as revenue weakened in the three months through June.

Rivals Mizuho Financial Group and Sumitomo Mitsui Financial Group saw bigger drops with their earnings in the period dropping 38 percent and 20 percent respectively.

The trio had warned that they would not repeat last year's bumper profits which were largely driven by a 57 percent return in the Nikkei stock index -- its best annual run in more than four decades.

Japanese banks hold vast stock holdings which benefited when overseas investors poured billions of dollars into the long-overlooked market, as a government economy blitz helped pushed down the value of the yen.

The currency's weakness lifted profits among Japanese firms that do business overseas.

The lenders may get a boost as government infrastructure plans in the aftermath of the 2011 quake-tsunami disaster as well as new building projects for Tokyo's hosting of the 2020 Olympics stimulate demand for loans.

The firms have also pointed to stronger fee income from financial product sales and a reduction in bad loans as bright spots.

But the Nikkei is sitting about four percent below its 2013 closing high and some of the shine is coming off Prime Minister Shinzo Abe's growth drive, dubbed Abenomics, as concerns mount over the strength of Japan's recovery.

Uncertainty about the economy may hold back borrowing by firms and individuals, after Japan raised its sales tax on April 1 for the first time in 17 years.

There were fears the levy hike -- seen as crucial to chopping a massive national debt -- would weigh on consumer spending and hold back the wider economy.

Japanese lenders have been cutting back on their reliance on domestic government bonds -- a key profit driver in recent years -- as the Bank of Japan's huge bond-buying measures announced in April start to reshape the country's debt markets.

The BOJ's programme, which is a cornerstone of Tokyo's bid to overcome years of deflation, unsettled the domestic debt market, prompting Japanese banks to further trim their exposure.

On Thursday, Mitsubishi said it expected a slightly weaker full-year net profit of 950 billion yen.

Mizuho booked a 154.7 billion yen net profit for the latest quarter as revenue shrank 10 percent to 704.7 billion yen.

Sumitomo said its net profit fell 20 percent to 230.8 billion yen.