The US has imposed financial sanctions on four Zimbabweans, including the son of President Emmerson Mnangagwa.

It accuses Emmerson Mnangagwa Junior of being linked to the businessman, Kudakwashe Tagwirei, who is already under US sanctions for alleged corruption.

The Treasury Department says over the last five years, Mr Tagwirei has used a combination of opaque business dealings and his ongoing relationship with the president to grow his business empire dramatically and rake in millions of dollars.

President Mnangagwa is already under US sanctions.

In a statement, the Treasury Department urged Zimbabwe's government to address what it called the root causes of many of the country's ills, including corrupt elites abusing institutions for their personal benefit.