WASHINGTON, Feb. 2 (Xinhua) -- The United States is imposing restrictions on the export of defense articles and services to South Sudan,U.S. State Department spokesperson Heather Nauert said Friday.

The United States is "appalled by the continuing violence in South Sudan," she said in a statement, accusing the South Sudanese government and "armed opposition" of continued use of military force "to seek political advantage."

The United States encourages the African Union to consider sanctions against those responsible, and is seeking support for a United Nations Security Council embargo on all arms flows into South Sudan, Nauert said.

South Sudan has been embroiled in a four-year conflict that has taken a devastating toll on the people, creating one of the most severe refugee crises in the world.

A peace deal was signed in August 2015 under UN pressure, but it was shattered by renewed fighting.