UPDATE 1-Amkor raises Q4 revenue outlook; shares rise

* Sees Q4 revenue up 6 pct sequentially

* Sees Q4 gross margins around 26 pct

* Shares up 8 pct in post-market trade

Dec 21 (Reuters) - Amkor Technology Inc (AMKR.O), a microchip packaging and testing company, raised its fourth-quarter revenue outlook citing better-than-expected customer demand across product lines.

The company, whose customers include whose customers include Toshiba Corp (6502.T) and IBM (IBM.N), said it expects revenue to rise 6 percent sequentially. It previously forecast revenue to be sequentially flat, plus or minus 2 percent.

The company also expects fourth-quarter gross margins to be about 26 percent, up from its previous outlook of 23 percent to 25 percent.

Analysts expect revenue of $610.95 million for the quarter, according to Thomson Reuters I/B/E/S.

Shares of the Chandler, Arizona-based company were up 8 percent at $7.05 in after-hours trade. They closed at $6.51 Monday on Nasdaq. (Reporting by Manasi Phadke in Bangalore; Editing by Ratul Ray Chaudhuri)