TOKYO: Tokyo stocks fell Friday morning as energy firms were hit by an OPEC decision not to deepen output cuts seen as crucial for boosting oil prices.

Investors were also disappointed that the Organization of the Petroleum Exporting Countries decided not to prolong the existing production cuts past March, which sent crude futures plunging almost five percent on Thursday.

"Clearly what was announced has not been enough, for now anyway," David de Garis, director of economics at National Australia Bank, said in a commentary.

The probe into possible collusion between US President Donald Trump's campaign and Russia in the November election "is deterring Japanese shares from moving higher", Okasan Online Securities said in a commentary.

Markets appeared to ignore data that showed consumer prices rose again in April due largely to higher energy bills.

Tokyo's benchmark Nikkei 225 index slipped 0.26 percent, or 51.02 points, to 19,762.11 by the break, while the Topix index of all first-section issues fell 0.28 percent, or 4.45 points, to 1,573.97.

Oil explorer Inpex dropped 2.13 percent to 1,029 yen and petroleum refiner Idemitsu lost 0.45 percent to 3,250 yen.

Toyota fell 0.26 percent at 5,969 yen and bank Mitsubishi UFJ slipped 0.22 percent to 699.9 yen.

The dollar weakened to 111.57 yen from 111.85 yen in New York.