* Fate of detainees key sticking point in peace talks
* Four others could be freed after "clarification"
* Donor Norway tells Uganda to start withdrawing troops (Adds Norway telling Uganda to withdraw troops, quotes)
By James Macharia and Richard Lough
NAIROBI, Jan 29 (Reuters) - South Sudan freed seven senior political figures on Wednesday who had been arrested on suspicion of plotting a coup, partially meeting a rebel demand at peace talks focused on ending weeks of fighting.
It handed them over to neighbouring Kenya and said four remaining detainees could be released after unspecified "legal clarifications" - raising hopes it was preparing to remove a major sticking point in troubled negotiations.
President Salva Kiir accused his former vice president Riek Machar of starting fighting between rival groups of soldiers in the capital Juba in mid December in a bid to seize power - a charge denied my Machar.
Authorities detained the 11 men, including former justice minister John Luk Jok, on suspicion of being involved, as clashes between government troops and now rebel fighters loyal to Machar quickly spread, killing thousands.
Washington, the United Nations, regional and Western powers - fearing the eruption of a full civil war in an unstable region - pushed both sides to start talks in Ethiopia and urged the government to respond to Machar's demand to free detainees.
"We don't feel bitter, we don't feel the president is our enemy," former justice minister Jok told reporters in Kenya's capital Nairobi after his release. Former finance minister Kosti Manibe was also among the seven freed.
South Sudan's current Justice Minister Paulino Wanawilla Unago had prepared the ground for the release on Tuesday, saying no evidence had been found against the seven.
But he did say that others, including Machar, could still face treason charges - a prosecution that could still disrupt peace efforts.
More than half a million have been uprooted from their homes in the clashes that spread to oil-producing areas - South Sudan has sub-Saharan Africa's third largest crude reserves according to BP.
Both sides signed a ceasefire on Thursday but have since accused the other of continuing the violence in the world's newest nation, which seceded from Sudan in 2011.
South Sudan's foreign minister Barnaba Marial Benjamin said on Wednesday authorities were still waiting for clarification on statements relating to the four remaining detainees.
"They will definitely be released once you get full satisfaction on the issues," he told Reuters in Addis Ababa, without giving a timeframe.
Kiir received military backing from neighbouring Uganda - a development that raised fears the clashes could deteriorate into a regional conflict.
One of Sudan's main donor's Norway said on Wednesday it was now time for Uganda to start withdrawing its troops from South Sudan to avoid worsening the crisis.
Foreign minister Benjamin told reporters on Wednesday there was a chance that could happen once the conflict ended.
"With the cessation of hostilities now there is a light at the end of the tunnel, and [the prospect] that peace and calm will come to the Republic of South Sudan ... and that we will not need the additional involvement of Ugandan troops," he said.
(Addtional reporting by Aaron Maasho in Addis Ababa and Andrew Green in Juba; Writing by Richard Lough; Editing by Andrew Heavens)