A former Navy chief was indicted Tuesday on charges of receiving bribes from the head of a troubled defense firm when he was in office seven years ago, state investigators said.

Retired Adm. Jung Ok-geun, who served as the Navy Chief of Staff from 2008 to 2010, allegedly asked for 770 million won ($699,000) in bribes from two affiliates of STX Group in September 2008, a government anti-corruption task force said.

Investigators believe Jung offered the companies Navy contracts to build a high-speed guided missile patrol gun boat and the next-generation frigate in return.

The bribes were allegedly provided in the form of a sponsorship to a yacht event arranged by Jung's son, according to the investigators.

The yacht company whose majority stake was owned by the younger Jung went out of business shortly thereafter, raising suspicions that it may have been a paper company.

Investigators said Jung initially asked for 1 billion won but settled for less after the STX chairman Kang Duk-soo balked. He also offered the chairman a chance to ride a warship with then President Lee Myung-bak.

Investigators also believe Jung at one point threatened the chairman, suggesting retaliation if he didn't oblige.

Jung's son, a former Navy officer, and a non-executive director of an STX Group affiliate were also indicted without physical detention for collusion. (Yonhap)