Tokyo stocks opened slightly lower on Tuesday with energy-linked firms slipping on lower oil prices as a stronger yen put the brakes on automaker shares.

The Japanese market has slipped from nearly two-year highs this week while Wall Street retreated from records on Monday.

Investors were cautious ahead of the British general election on Thursday, after deadly terror attacks in London.

A European Central Bank meeting and testimony by ex-FBI director James Comey, whom President Donald Trump fired last month amid a probe of his campaign's ties to Russia, are also awaited. 

"There a strong sense of wanting to wait-and-see among investors ahead of former FBI director Comey's testimony and the UK elections," said Yutaka Miura, a senior technical analyst at Mizuho Securities.

"With both US shares and Japanese shares trading near fresh highs, there's no need to jump on the bandwagon now, ahead of key events," he told Bloomberg News.

Tokyo's benchmark Nikkei 225 index slipped 0.22 percent, or 44.66 points, to 20,126.16 in early trade while the Topix index of all first-section issues was down 0.20 percent, or 3.26 points, to sit at 1,606.71.

On forex markets, the dollar was weaker at 110.12 yen from 110.48 yen in New York.

The stronger yen dented some exporting firms with automaker Toyota falling 0.18 percent at 5,957 yen and rival Nissan slipping 0.13 percent to 1,078.5 yen.

Petroleum-linked shares dropped following another overnight drop in crude prices.

Energy explorer Inpex lost 0.34 percent to trade at 1,024.5 yen and refiner Idemitsu dropped 2.30 percent to 3,185 yen.