Tokyo stocks finished slightly lower Tuesday to extend their decline to a third straight session, wieghed down by slides in key exporters due to the yen's strength. The Nikkei Stock Average closed at 8,488.09, down 20.23 points, or 0.24%. It is the first time for the benchmark index to end the day below 8,500 since June 8, when it finished the session at 8,459, according to (Nikkei) website. Overseas markets declined overnight as yields on Spanish and other government bonds rose on concerns about Europe's sovereign debt crisis. The yen's continued advance prompted investors to sell leading exporters to avoid risk in Tokyo. The Nikkei average briefly turned higher as investors moved to buy attractively priced stocks and cover their short positions after Wall Street trimmed its losses overnight. But aggressive buying was short-lived. Trading value on the first section of the Tokyo Stock Exchange totaled 900.1 billion yen, falling short of 1 trillion yen for the sixth straight session.