SEATTLE (Reuters) - The mother of imprisoned American missionary Kenneth Bae has arrived in North Korea to visit her ailing son, who was sentenced to 15 years of hard labor in May on charges of state subversion, his family said in a statement released on Thursday.

The statement, which also asked the North Korean authorities for mercy, said that Myunghee Bae expected to be in North Korea for about five days for a trip in which she aimed "to encourage her son, who is imprisoned and has become ill."

(Reporting by Eric Johnson; Writing by Cynthia Johnston)