TOKYO, Dec 7 (Reuters) - Japan's Nikkei index racked up its biggest gain in more than a month on Tuesday, as worries over the impact of the Omicron coronavirus variant eased, aiding investors to buy bargains, such as SoftBank Group and travel-related stocks.

The Nikkei share average ended 1.89% higher at 28,455.60, marking its biggest percentage gain since Nov. 1. The broader Topix advanced 2.17% to 1,989.85.

Japan shares also tracked Wall Street higher as investors cheered some optimistic comments from a top U.S. official on the latest variant.

"We have more details on the Omicron and it seems that impact would not be that serious. That has given a relief to investors," said Kazuharu Konishi, head of equities at Mitsubishi UFJ Kokusai Asset Management.

SoftBank Group, the global tech investor that dragged down the Nikkei in the previous session, jumped 7.94% and was the biggest percentage gainer on the index.

Shares that would benefit from an economic reopening rose, with airlines and railway operators leading gains among the exchange's 33 industry sub-indexes, up 4.17% and 3.06%, respectively.

Japan Airlines rose 4.6% and West Japan Railway gained 4.97%.

Travel-related online services Open Door surged 7.66% and Airtrip also gained 7.66%.

"The markets have been volatile globally. But these volatilities suggest that the market is moving by bets from short-term investors," said Shigetoshi Kamada, general manager at the research department at Tachibana Securities.

There were 218 advancers on the Nikkei index against 6 decliners.

Nippon Suisan Kaisha fell 5.6% and was the biggest loser, followed by Z Holdings, losing 2.7% and Konami Holdings, which fell 1.29%. (Editing by Uttaresh.V)