Some 145 child soldiers fighting for two rebel groups in South Sudan have been released, Unicef has announced.

The children were recruited by the Cobra Faction and the SPLA In Opposition, two armed groups which have been fighting the government.

They were freed in the eastern region of Pibor and "disarmed and provided with civilian clothes," Unicef said in a statement.

About 16,000 children are still in "armed groups", it says.

Unicef said it was the largest release of child fighters since last year but warned that children were still being recruited by various armed groups.

Mahimbo Mdoe, Unicef's representative in South Sudan urged all parties to "end the recruitment and to release children who are currently serving in their ranks".

Child soldier case study: Silva, 11 years old:

I have been fighting for more than two years. I haven't seen my mother and father since last summer.

I've seen many people killed when I was on missions.

I had an AK-47. It was heavy. I was fighting to protect my family and village.

Now I want to go to school and learn. I don't want to fight anymore, I was scared.

South Sudan plunged into internal strife in December 2013 when President Salva Kiir accused his rival, former Vice-President Riek Machar of plotting a coup.

The two camps have broken a series of peace deals, the latest one in July, meant to resolve the crisis in the country

Hundreds of civilians have been killed and thousands forced from their homes in the latest fighting.