Tokyo stocks closed lower on Thursday as a weak lead from Wall Street overnight after oil prices retreated set a negative tone, with a dour market mood compounded by ongoing geopolitical concerns centered on the Korean Peninsula.

The 225-issue Nikkei Stock Average dropped 87.57 points, or 0.44 percent, from Wednesday to close the day at 19,994.06, marking the first time in three weeks the index has fallen bellow the psychologically important 20,000 line.

The broader Topix index of all First Section issues on the Tokyo Stock Exchange, meanwhile, lost 3.10 points, or 0.19 percent, to finish the day at 1,615.53.

Oil and coal product, mining and rubber product-linked issues comprised those that declined the most by the close of play, and declining issues outpaced advancing ones by 1,006 to 861 on the First Section.

Trading volume on the main section on Thursday came to 1,683.08 million shares, dropping from Wednesday's volume of 1,794.61 million shares.

The turnover on the penultimate trading day of the week totaled 2,310.5 billion yen (20.45 billion U.S. dollars).