President Barack Obama is telling his South Korean counterpart that the U.S. stands "shoulder to shoulder" with its close ally and will work with the international community to strongly condemn what the White House branded as an "outrageous" attack by North Korea that killed two South Korean marines.

Obama called South Korean President Lee Myung-bak (lee myuhng bahk) following a meeting with his national security advisers to discuss the attack early Tuesday on a South Korean island that set off an exchange of artillery.

The White House says the two presidents agreed to hold combined military exercises and enhanced training in the days ahead to continue the close security cooperation between the two countries.