The US government has called on South Korea to arrest a brother of former UN Secretary-General Ban Ki-moon who is being implicated in a corruption scandal.

Assistant US Attorney Daniel Noble told a federal court on 20 January that a request has been made for the arrest of Ban Ki-sang who is being accused of accepting bribes to carry out the sale of a Vietnamese building complex.

Ban Ki-sang was an executive at South Korean construction firm Keangnam Enterprises Co Ltd when he allegedly committed the crime. Noble said the US also plans to seek his extradition, "but as of yet, he has not been apprehended".

According to South Korean news agency Yonhap, the Justice Ministry is still discussing the request but "it is not yet a formal consultation".

An indictment unsealed on 10 January accuses Ban Ki Sang and his son Joo Hyun Bahn, a Manhattan real estate broker, over the attempted $800m (£646m) sale of a building in Hanoi owned by Keangnam.

It is believed that the international bribery conspiracy took place between March 2013 and May 2015 when the accused tried to get an official from an undisclosed Middle Eastern kingdom to purchase the property.

According to prosecutors, the father-son duo offered to pay an initial bribe of US$500,000, wired to an account in New York from South Korea in April 2014, followed by a payment of US$2m upon completion of the sale.

Malcolm Harris, a US citizen has been accused of masquerading as a go-between for the deal. According to the indictment, he pocketed the bribe and spent it on luxury purchases for himself.

The whole scandal has put a damper on Ban Ki-moon's own political ambitions. On 21 January he once again apologised for his family's involvement in the corruption case.

In his statement, he said he hoped that discussions between South Korea and the United States – if they were taking place as reported – would be "strict and transparent" so as to remove any suspicion left in the minds of the South Korean public.