A South Korean group campaigning for the return of Korea's national treasures and artifacts abroad has reached out to the White House in a bid to get its voice heard.

The International Organization on Retrieval of Korean National Treasures Inc. filed an online petition with the "We the People" page of the White House website.

It asked the U.S. to formally return the Joseon Dynasty (1392-1901) Royal Seal and several other Korean treasures apparently stolen by American soldiers during the 1950-53 Korean War.

The group said President Barack Obama's trip to Seoul, slated for April, provides a good chance for the return.

"The Chosun Dynasty Royal Seal is a highly acclaimed National Treasure that was housed in a Royal Palace in Seoul," it said in the petition. "During the Korean War the National Royal Seal was illegally taken out of the country by the U.S. military personnel."

Last November, the U.S. Immigration and Customs Enforcement's Homeland Security Investigations said it seized nine seals from the Joseon Dynasty and the Korean Empire (1897-1910) believed to be illegally obtained by an American soldier during the Korean War.

The nine seals include three national seals of the Korean Empire, one royal seal of the Korean Empire and five signets of the royal court of the Joseon Dynasty, according to the U.S. agency.

South Korean officials also said a 16th century royal seal in the collection of the Los Angeles County Museum of Art might have been stolen out of a shrine in Seoul during the war. (Yonhap)