The first civilian deaths from the clash between North Korea and South Korea were confirmed Wednesday. South Korean troops remained on high alert, and buildings continued to burn on Wednesday.
Rescuers found the burned bodies of two people who live on the island of Yeonpyeong near the disputed sea border with North Korea. Two South Korean Marines were also killed during the exchange of gunfire between the two countries.
President Barack Obama is planning on meeting with Defense Secretary Robert Gates Wednesday to talk about escalating tensions there.
Obama underlined Washington's pledge to "stand shoulder to shoulder" with Seoul and called upon China to restrain ally North Korea.
China - North Korea's closet ally and its largest supplier of aid - said late Wednesday it was "highly concerned" about the exchange and urged restraint.
China "feels pain and regret about an incident causing deaths and property losses and is worried about the developments," Foreign Ministry spokesman Hong Lei said in a statement. "We have always maintained that the relevant parties should, through dialogue and consultation, resolve disputes by peaceful means."
During an exclusive interview with Barbara Walters, the president was asked if the North Korean attack on South Korea was an attack on the U.S.
"South Korea is our ally," Obama said. "It has been since the Korean War, and we strongly affirm our commitment to defend South Korea as part of that alliance."
The Associated Press contributed to this story.