Japanese stocks tumbled to 1-1/2-week lows on Thursday morning on worries that allegations against the US President Donald Trump over his interference with a federal investigation would delay his efforts on tax cuts and economic stimulus.

The Nikkei share average dropped 1.8 per cent to 19,457.75 after falling to as low as 19,449.73, the lowest since May 2.

A small but growing number of Trump's fellow Republicans called on Wednesday for an independent probe of possible collusion between his 2016 campaign and Russia, and one even mentioned impeachment.

A strong Japanese gross domestic product data released in the early morning was offset by the White House turmoil, which dragged down Wall Street sharply overnight, where the S&P 500 and the Dow Jones Industrial Average notched their biggest one-day fall since Sept. 9.

“This GDP data could have been a catalyst for the Nikkei to touch the 20,000 mark if Trump's turmoil did not come at this time,” said Masayuki Doshida, a senior market analyst at Rakuten Securities. “Fears that US stocks may fall further in the future are keeping investors nervous.”

According to government data, Japan's economy expanded at the fastest pace in a year in the first quarter.

Financials were the biggest hit, with all the insurance , securities and banking sectors plunging more than 3 percent.

Dai-ichi Life Holdings dived 5 per cent, Sompo Holdings stumbled 3.4 per cent, Nomura Holdings shedding 4 per cent and Mitsubishi UFJ Financial Group declining 3.8 per cent.

Exporters were hammered after the dollar fell to a three-week low of 110.53 yen on Thursday.

Honda Motor Co and Subaru Corp both dropped 2.3 per cent, Tokyo Electron, Fanuc Corp and TDK Corp all tumbled around 3 per cent.

Utility shares outperformed, after Kansai Electric Power Co said that it will restart the No.4 reactor at its Takahama nuclear plant.

Kansai was flat, Chugoku Electric Power rose 0.1 per cent and Hokuriku Electric Power added 0.3 per cent.

The broader Topix dropped 1.7 per cent to 1,549.01 and the JPX-Nikkei Index 400 declined 1.7 per cent to 13,822.74.