South Sudan conflict: Machar in Khartoum on 'humanitarian grounds'
Machar was replaced by Taban Deng Gai as South Sudan's first vice president after hundreds died in Juba last month in clashes between Machar's forces and government troops.
"Sudan has received Riek Machar on humanitarian grounds and so he can have medical treatment," Sudanese government spokesman Ahmed Bilal said in a statement.
He did not specify when Machar arrived in Khartoum, but said that he was in need of "immediate medical treatment."
"He is now stable. He will continue to stay in the country until he decides when to leave," Bilal said, without providing further details on the treatment.
Machar's absence after fleeing renewed fighting in South Sudan's capital last month struck another blow to the country's peace deal to end a civil war.
Reports emerged on Tuesday of at least 275 people were killed in fighting between government and rebel forces in South Sudan.
Rebels attacked army barracks in the northeast town of Pajut on Friday, Jonglei Governor Phillip Aguer said.
At least 242 opposition and 23 government forces were killed and 10 civilians died in the crossfire, he added.
But a spokesman for the rebels, James Gatdet, said the army launched the offensive and more than 300 soldiers and 30 rebels were killed.
South Sudan's Civil War
After a 1983-2005 civil war, the mainly Christian south of Sudan split from the Muslim north on 9 July 2011, following a referendum six months earlier.
But in December 2013 a brutal civil war erupted in the world's youngest country between supporters of President Salva Kiir and Machar, after Kiir accused his deputy of plotting a coup.
Ties between Khartoum and Juba have strained since then amid allegations that Sudan backs Machar in the civil war that has killed tens of thousands and forced more than two million from their homes.
|The civil war in South Sudan has killed tens of thousands and forced more than two million out of their homes|
Sudan's announcement of Machar's presence in Khartoum comes just a day after Deng wrapped up his first official visit to Khartoum.
South Sudan's ambassador to Khartoum Mayan Dout confirmed that Juba had been informed about Machar's presence in Sudan.
"The government of Sudan informed Vice President Taban Deng that it had received Riek Machar on humanitarian grounds," Dout told AFP.
He added that President Salva Kiir was informed of Machar's presence in the Sudanese capital.
The civil war in South Sudan has split the country along ethnic lines and driven it to the brink of collapse.
A peace deal signed between the government and rebels almost a year ago has so far failed to end the conflict.
Agencies contributed to this report.