WASHINGTON, May 22  -- The United States on Thursday urged the Democratic People's Republic of Korea (DPRK) to refrain from "provocative actions" after it fired two rounds of artillery shells near a patrol ship of the Republic of Korea (ROK).

"We urge North Korea to refrain from provocative actions that aggravate tensions and instead focus on fulfilling its international obligations and commitments," State Department spokeswoman Jennifer Psaki said at a daily news briefing.

The DPRK allegedly fired several rounds of artillery shells toward waters in ROK Thursday, and two of them fell near a ROK patrol ship sailing around the western maritime border, prompting the ROK side to fire back. No injuries and damage have been on the ROK patrol ship.

"We continue to urge North Korea to exercise restraint and take steps to improve its relations with its neighbors," Psaki said, adding Washington was "closely" monitoring the situation on the Korean Peninsula.