By Joshua Hunt

TOKYO, Dec 21 (Reuters) - Japanese stocks fell in thin trading on Monday morning as the yen gained against the dollar, putting pressure on exporters after the Bank of Japan disappointed markets with minor adjustments to its massive stimulus programme.

The Nikkei share average fell 1.7 percent to 18,673.72 during midmorning trading.

"Markets weren't impressed by the BOJ's actions on Friday and currently that alone is enough to see the index capitulate," said Martin King, co-managing director at Tyton Capital Advisors.

"I don't think we are going to see 18,565 breached this year but a macro environment of sociopolitical unrest, terror, commodity price volatility and central bank intervention will have many investors exercising caution as the exuberance of the past three years is nowhere to be seen."

On Friday, the BOJ announced it would maintain its massive stimulus while expanding the types of assets it purchases - a move some investors believe might delay expansion of the quantitative easing programme which has underpinned stocks.

Sentiment took a further hit as U.S. crude oil prices dipped toward last week's 2015 lows after a rebound in drilling activity threatened to add to the current glut.

Major exporters suffered on the yen's extended gains against the dollar. Panasonic Corp shares fell 3.7 percent in midmorning trading while Bridgestone Corp slipped 1.4 percent and Toyota Motor Corp fell 2.3 percent.

Toshiba Corp's shares tumbled as much as 10.4 percent to its lowest in more than three years after weekend media reports said the company would soon announce record losses of around 500 billion yen ($4.13 billion) for the year ending in March.

Sharp Corp bucked the broader market, climbing 1.7 percent after the Nikkei business daily reported that U.S. buyout firm KKR & Co was among the private equity firms interested in investing in the Japanese firm.

The broader Topix fell 1.5 percent to 1,514.62 with all of its 33 subindexes sitting in negative territory.

The JPX-Nikkei Index 400 slipped 1.4 percent to 13,637.41.

($1 = 121.1300 yen) (Reporting by Joshua Hunt; Editing by Shri Navaratnam)