TOKYO, April 4 (Reuters) - Japan's Nikkei share average fell on Tuesday to 10-week lows as the safe-haven yen rose and as automakers tumbled on weaker-than-expected U.S. sales.

Financial stocks such as banks and insurers, which seek to boost returns from higher yielding U.S. bonds, also lost ground after yields on 10-year U.S. Treasury notes overnight fell to the lowest level since Feb. 27.

The Nikkei dropped 0.9 percent to 18,810.25 points, the lowest closing level since Jan. 24.

The dollar extended overnight losses and was down 0.4 percent at 110.51 yen after hitting 110.370, its lowest in a week, as investors are cautious before the upcoming meeting between U.S. President Donald Trump and Chinese President Xi Jinping, while sentiment was soured by suspected suicide bombing in St. Petersburg, Russia.

The broader Topix dropped 0.8 percent to 1,504.54 and the JPX-Nikkei Index 400 declined 0.8 percent to 13,463.23. (Reporting by Ayai Tomisawa; Editing by Kim Coghill)