Tokyo stocks opened lower on Wednesday as the yen remained firm with investors cautious ahead of major events including the British general election.

The British vote, the European Central Bank's policy meeting and testimony by ex-FBI director James Comey, whom US President Donald Trump fired last month amid a probe of his campaign's ties to Russia, are all happening on Thursday.

Even though many investors are not expecting a change of government in London, they remain wary after the shock Brexit vote, Mitsuo Shimizu, equity strategist at Japan Asia Securities, told Bloomberg News.

The benchmark Nikkei 225 index fell 0.10 percent, or 20.64 points, to 19,959.26 in early trade while the Topix index of all first-section issues was down 0.16 percent, or 2.53 points, at 1,593.91.

The dollar remained weak after it dipped below the psychologically important 110 yen level for the first time in the past six weeks on Tuesday.

The greenback fetched 109.44 yen in early Wednesday trade, against 109.42 yen in New York Tuesday afternoon.

Some exporters were down on a firm yen, with Honda dipping 0.73 percent to 3,089 yen and its bigger rival Toyota falling 0.47 percent to 5,882 yen in early trade.