South Sudan President Salva Kiir has granted amnesty to rebel leader Dr Riek Machar and others across the country.

"I declare republican order number 14 for the year 2018 for the grant of general amnesty to the leader of SPLM-IO Dr Riek Machar and other estranged groups who waged war against the government of the republic of South Sudan," read the order broadcast by the state media late Wednesday.

President Kiir also ordered the army to allow unrestricted access to humanitarian agencies to respond to massive humanitarian needs across the country and to respect the ceasefire.

President Kiir and Dr Machar last Sunday signed an accord on governance and security arrangements after a round of peace talks in the neighbouring Sudan's capital, Khartoum.

This is the second agreement after a similar peace deal signed in 2015 fell apart a year later in deadly clashes that saw Dr Machar flee into exile.

The two have committed themselves to implement the peace deal.

South Sudan attained independence from Sudan in 2011 but descended into a civil war two years later.

The war erupted following a power wrangle between President Kiir and his former deputy Dr Machar.

The conflict has caused one of the largest humanitarian crises in the continent, according to the UN.

The fighting has killed thousands, displaced millions and affected neighbouring countries.