The nation's top court on Thursday acquitted a North Korean defector indicted on charges of spying for Pyongyang, citing a lack of evidence.

Yoo Woo-seong, 35, was indicted in February 2013 over allegations he collected detailed information on defectors in the South while working at the Seoul city government and relayed it to the North in breach of the country's National Security Law, which prohibits South Koreans from engaging in activities benefiting the North.

Upholding a lower court's ruling, the Supreme Court found Yoo not guilty of charges he carried out espionage activities, citing a lack of admissibility in the testimony of the witness.

The court, however, found him guilty of other charges including fraud and passport law violation and sentenced him to a year in prison with two years of suspension. Yoo was also ordered to forfeit some 25 million won (US$21,800) he gained with the status as a defector.

Under South Korean law, Yoo, who held Chinese nationality in North Korea, cannot be acknowledged as a North Korean.

After a Seoul district court acquitted Yoo in August 2013, prosecutors appealed the verdict and submitted Chinese immigration records on Yoo's visit to the North. But some of the documents were

later found to have been forged to frame Yoo. 

In 2014, prosecutors announced the results of a two-month investigation into the scandal, concluding that the National Intelligence Service fabricated the immigration records.

Later on Thursday, the court will announce the ruling on the officials who are involved in the forgery of the documents. (Yonhap)