TAIPEI, Aug 22 (Reuters) - Shares of Mega Financial Holding , one of Taiwan's biggest banks, opened 5 percent lower in Taipei on Monday after its New York banking branch was fined $180 million by New York State's financial services department for anti-money laundering violations that included lax attention to risk exposure in Panama.

Taiwan's premier Lin Chuan has ordered an investigation to determine who should be held responsible for the violations at state-run Mega Financial.

(Reporting by Faith Hung; Editing by Kenneth Maxwell)