By George Hakim

JUBA, July 29 (Reuters) - South Sudan's new vice president, Taban Deng Gai, poured scorn on his predecessor Riek Machar and suggested he go into exile, deepening a rift at the heart of the political elite that has raised the risk of more turmoil after months of fighting.

"Something is wrong with comrade Riek," Gai said in a speech broadcast on national television and radio, as he formally took office on Thursday.

Machar, the previous vice president, and the SPLM-IO group he leads, have been caught up with more than two years of on-and-off, ethnically charged fighting with supporters of the country's President Salva Kiir.

Machar returned to the capital Juba in April after a shaky peace deal, but left again this month when new clashes broke out.

Nothing has been heard from him since and Kiir replaced him as vice president last week with Gai, a former ally of Machar's.

"I am advising him (Machar) to come back to Juba and stay peacefully or he can go anywhere; to Addis Ababa to Nairobi to Kampala or Khartoum to stay there peacefully and wait for elections (in 2018) so that you the people come and elect him to office or you say we don't trust you," Gai said.

Politics have long been plagued by splits and rivalries as leaders switch allegiances in a complex contest for power and influence in the oil-producing nation, which only gained independence from Sudan five years ago.

Members of the SPLM-IO loyal to Machar accused Kiir on Friday of stockpiling weaponry, including surface-to-air missile batteries, around Juba in "a serious and direct threat to the national security".

Government military spokesman Lul Ruai Koang declined to comment on the detail of the accusation but said the army was authorised "to strengthen our air defence capability and to defend the territorial integrity of this country". (Addtional reporting by Denis Dumo in Nairobi; Writing by George Obulutsa; Editing by Andrew Heavens)