South Sudan's government and rebels are to sign a ceasefire shortly, mediators in Ethiopia say.

The talks had been deadlocked over the issue of 11 political detainees, whom the rebels want to be freed before discussing a ceasefire.

In the past week, government forces have recaptured the two main cities under rebel control.

More than 500,000 people have been forced from their homes during the month-long conflict.

What started out as a political dispute between President Salva Kiir and his former deputy Riek Machar on 15 December has escalated into full-scale conflict, with reports of ethnic killings.

Mediators said they expected the rival parties to sign agreements on the "cessation of hostilities and the question of the detainees" at the hotel in Ethiopia's capital, Addis Ababa, where the talks have been taking place.

The rebels have been demanding the release of Mr Machar's political allies, prominent political figures from a faction of the governing SPLM party.

They were detained when Mr Kiir first made the allegations of an attempted coup - which Mr Machar denies.

Another key rebel demand was for Ugandan troops fighting alongside the government forces to be withdrawn.

Last week, the UN human rights chief said both government soldiers and rebels had committed atrocities in South Sudan, one of the world's poorest countries.

More than 70,000 civilians are seeking shelter at UN bases across South Sudan and the UN estimates that considerably more than 1,000 have been killed.

Following the outbreak of hostilities, it was agreed to boost the UN force and an extra 5,500 peacekeepers are being deployed to South Sudan, to bring its strength up to 12,500.