South Sudan must release political prisoners before peace talks can begin: Japanese ambassador

The Japanese ambassador has urged South Sudan's president to kick start peace talks by releasing political prisoners.

Kiya Masahiko met President Salva Kiir on Wednesday at the State House in the South Sudan capital Juba to discuss the "agenda and outcomes" of peace talks, referred to as the National Dialogue.

"The Japanese government and people hope to see South Sudanese leaders take 'concrete steps' towards achieving peace in the country," Masahiko said.

The ambassador reportedly urged the president to work towards a ceasefire by releasing prisoners early and allowing the free movement of aid agencies in South Sudan.

The government has detained thousands of people since fighting broke out in the "world's youngest country" last summer, with widespread allegations of torture and humanitarian abuse.

Tens of thousands of people have died in the fighting and millions more have fled the country. The UN has warned of genocide.

There are more than 60 tribal groups in South Sudan and the violence has largely fallen along ethnic lines.

South Sudan's Dinka-majority government troops have been known to attack the mostly Nuer opposition since indepenence from Sudan in 2011.

The National Dialogue peace process was launched in May as a government-led process to re-engage with the country's rebels.

Dialogue members visited the rebel chief, Riek Machar, in South Africa in June to discuss terms.

Rebel chiefs have routinely called for a ceasefire and the release of political prisoners as key demands.