The U.S. army on Wednesday extended a curfew for military personnel in South Korea by two months, a day after a court sentenced an American soldier to 10 years in prison for sexually assaulting a local teenage girl.

I firmly believe that military discipline is the foundation of mission-ready, well-trained and effective organisations, U.S. Forces Korea commander Gen. James Thurman said in a statement.

We must maintain mission readiness and the strength of the Republic of Korea-U.S. alliance.

The United States has about 28,000 troops in South Korea in the allies' defence against North Korea, which was accused of mounting two attacks against its southern neighbour last year that killed 50 people. The South has about 650,000 active force soldiers.

On Tuesday, South Korea's Uijeongbu District Court said in a sentence that the severity of the crime committed against the rape victim allowed for the full term as laid out in the sentencing guideline.

The new curfew will be in place until January 6.

A 30-day curfew was initiated last month, days after allegations of two rape cases involving U.S. soldiers surfaced. Up until July last year, a similar curfew had been in place for nine years.

In 2002, the deaths of two schools girls hit by a U.S. military vehicle conducting exercises and the subsequent acquittal of U.S. soldiers involved in a U.S. court martial led to a massive public outcry and an outpouring of anti-American sentiment in South Korea.

(Reporting by Jeremy Laurence; Editing by Yoko Nishikawa)