JUBA: The government of South Sudan said on Friday that First Vice President Riek Machar was `under house arrest`, two days after he was detained, as a former Kenyan premier arrived in Juba to mediate the crisis threatening to end the fragile peace deal between rival factions.

Machar`s arrest by forces loyal to President Salva Kiir prompted UN chief Antonio Guterres to call on warring parties to `put down the weapons` and `put all the people of South Sudan first`, as the conflict risks plunging the world`s youngest nation back into civil war.

Kiir `directed the placement of Dr Riek Machar under house arrest`, information minister and government spokesman Michael Makuei Lueth said in a statement, in the first official comments since Machar`s detention.

Despite the arrest, Juba appeared calm on Friday, with shops open and people on the streets.

Makuei blamed Machar for clashes in recent weeks in Nasir county, accusing him of `agitating` his forces `to rebel against the government with the aim of disrupting peace so that elections are not held and South Sudan goes back to war`.

He called on the public`to be calm and maintain peace,` adding that Machar and his allies `will be investigated and brought to book`.

The unravelling powersharing deal between Kiir and Machar risks a return of the civil war that killed around 400,000 people in five years.

The deputy chair of Machar`s party said his arrest `abrogated` the agreement.

`The prospect for peace and stability in South Sudan has now been put into serious jeopardy, Oyet Nathaniel Pierino said in a statement on Thursday.

But Makuei insisted the peace agreement still stood. A convoy of 20 heavily armed vehicles entered Machar`s residence in the capital Juba late on Wednesday and arrested him, according to a statement issued by a member of his party.

On Friday, Machar`s party, condemned his `unlawful house arrest, calling it a government tactic to `derail the peace process and consolidate power through unconstitutional means`.

The party`s foreign relations committee chairman, Reath Muoch Tang, said Kiir`s party was planning to dissolve the government `under the pretext of a state of emergency`.-AFP