South Korea's impeached ex-President Park Geun-hye has been slapped with additional charges of taking $3.4 million from the country's spy agency, some of which were spent on personal bills and cosmetic injections.

The Seoul Central District Prosecutor's Office on Thursday indicted Park on the charges of bribery, loss of national funds and obstruction of duty, during her term.Park already stands trial on a string of 18 charges which include abuse-of-authority and extortion of funds from the country's conglomerates in cahoots with her long-time friend Choi Soon Sil.

Prosecutors say she received more than 3.6 billion won from the National Intelligence Service's blind budget set aside for confidential operations. Monthly payments ranging from $47,000 to $188,000 were paid to the ex-President from May 2013 to July 2016.

In September 2016, former NIS director Lee Byung-ho paid her $188,000 through her secretary Jeong Ho Seong, according to the prosecution.

Park is also accused of requesting ex-NIS chief Lee Byung Ho to pay her presidential secretary Lee Won Jong $141,000.

Prosecutors discovered some $3.1 million in NIS kickbacks had stashed away in the office of former presidential secretary Lee Jae Man who managed the money under Park's orders.

Nearly half the funds were spent for personal use, including a mobile phone and utility fees as well as medical treatments and cosmetic injections for Park and her close aides, including Choi Soon Sil.

Prosecutors also found evidence that some of the money supported a boutique owned by Choi, Hankyoreh reported.

The fund was also used to provide nearly $1 million in bonuses for Park's secretaries, Lee Jae-man, Ahn Bong Geun and Jeong Ho Seong.

Post-it notes found during the probe showed that a third of the sum approved by Choi.

While the ex-secretaries testified that the contents of the notes were true, the former president and Choi have refused to be questioned over the matter.