The nation's top court on Friday upheld the acquittal of a former Navy chief who was accused of corruption in a deal to supply parts for the country's indigenous salvage ship, citing a lack of evidence.

The Supreme Court found retired Adm. Hwang Ki-chul, who served as the chief of naval operations from 2013 to 2015, not guilty of pressuring his subordinates to forge a document in 2009 to help a firm win the contract.

Prosecutors suspected that he made them manipulate a quality assurance document for a sonar system built by the parts supplier for the country's first domestically built rescue and salvage ship. The supplier was introduced by a friend of then chief of Navy Chung Ok-geun, according to prosecutors.

Hwang, who was in charge of the nation's project to build the Tongyeong at the Defense Acquisition Program Administration, was suspected to have played a role in underhand dealings in order to get promoted.

The top court, however, said there is a lack of evidence proving that Hwang forged the document to give favors to the company, adding his alleged motive is unclear.

In August, a district court also acquitted Chung of allegations he orchestrated the scheme, citing a lack of evidence.

The 3,500-ton Tongyeong was found to be fraught with problems and failed to participate in rescue operations in a ferry tragedy in April 2014 that killed more than 300 people. (Yonhap)