The information about the house arrest came from President Salvar Kiir's spokesperson.
President Kiir and Machar have long been fighting over the real power in South Sudan, which led to a civil war breaking out in 2013 and lasting for five years.
Recently, the fragile peace has been close to being broken between the two rival groups.
The Minister of Information and spokesperson Michael Makuei Lueth referred to the fact that President Kiir has the right, according to the country's constitution, to put the vice president under house arrest.
UN Secretary-General António Guterres warned the parties in the conflict on Friday to "lay down their arms".
South Sudan has fallen off our radar screen, but that does not mean we can allow the country to fall into the abyss, said the UN chief.
