(Adds government response, recasts)

By Denis Dumo

JUBA Nov 17 (Reuters) - Both factions in South Sudan's civil war accused each other of violating a peace deal signed in August, after the country's rebels said on Tuesday that government soldiers had launched attacks against their positions in oil-rich Unity state.

Defence Minister Koul Manyang Juuk said government troops attacked the rebels in response to raids that the rebels had carried out last week in Unity, Bentiu and Malakal states that killed 22 people.

He said the attack violated a peace deal signed between President Salva Kiir and rebel leader and former government deputy Riek Machar.

"We are still optimistic that the peace agreement that we have signed with the rebel leader Riek Machar will be implemented," he told Reuters.

The world's youngest country descended into civil war in December 2013 when a row between President Kiir and Machar ended with fighting that often ran along ethnic fault lines between Kiir's Dinka and Machar's Nuer people.

Under pressure from its neighbours and from the possibility of sanctions, rebel leader Machar signed a peace deal on Aug. 17 and Kiir followed suit 10 days later, although both sides were quick to accuse each other of further attacks.

Rebel spokesman Col. William Gatjiath Deng said in a statement that in the latest attacks government troops hit eight of their positions in various parts of rebel-held territory in Unity State on Sunday and Monday.

"It's very unfortunate that these attacks happened at the time when the country is in need of peace and the advance team from the SPLM/A is preparing to visit Juba in order to sensitise the civil population about the signed peace accord between government and opposition," Deng said. The SPLM/A refers to the rebels.

"SPLA/Juba faction wants to gain more territories from us and this would jeopardise the peace deal," he added, referring to the government.

Machar is expected in Juba on Nov. 23 where he is due to meet South Sudan government leaders at a regional peace conference. It will be his first time back in the capital since the start of the civil war.

Unity State has experienced some of the worst fighting in the conflict that has killed thousands of people and displaced more than 2.2 million, 500,000 of whom have fled the country, according to humanitarian agencies. (Writing by George Obulutsa, Editing by Angus Berwick)