Nairobi - South Sudan's army has carried out "grave" human rights abuses in an all-out offensive that has cut off aid from half a million people, the regional bloc pushing peace efforts said on Friday.East Africa's eight-country Igad bloc condemned the "unwarranted and appalling actions" of the government, reporting "violence targeting civilians, grave human rights abuses and destruction of villages."The assault, which began in late April, is one of the heaviest government offensives in the 17-month long civil war, with gunmen raping, torching towns and looting aid supplies in the northern battleground state of Unity, according to the UN and aid agencies.The assault is now expanding into neighbouring states to the north and east."Government forces have been conducting full-scale military offensive against opposition forces in Rubkona, Mayom, Guit, Koch and Mayendit counties in Unity state," the Igad statement read."It is also increasingly clear that the offensive is being expanded into Jonglei and Upper Nile states."UN aid chief in South Sudan Toby Lanzer this week said the number of civilians left without "life-saving aid" due to the offensive in Unity alone had risen to 500 000, after the UN and aid agencies pulled out due to a surge in fighting."IGAD mediators are extremely dismayed at the credible reports... of acts of violence targeting civilians, grave human rights abuses and destruction of villages," the statement added, warning "there is no military solution" to the war.Girls raped, boys abducted Over half of the country's 12 million people are in need of aid, with 2.5 million people facing severe food insecurity, according to the UN.The US Agency for International Development (USaid) warned it was "extremely concerned about the welfare of South Sudanese who need humanitarian assistance and are out of reach."The UN peacekeeping mission has said that girls and women have been raped, while boys as young as 10 have been abducted as child soldiers. Aid groups said their bases had been ransacked.But South Sudan army spokesperson Philip Aguer said troops were fighting in "self-defence", and dismissed the reports or abuses, saying the army "has a code for operations that do not allow burning of villages or attacking innocent civilians."Fighting broke out in December 2013 when President Salva Kiir accused his former deputy Riek Machar of attempting a coup, setting off a cycle of retaliatory killings across the country.Over a year of talks mediated by Igad, the Inter-governmental Authority on Development, broke down in March.The violence, which has escalated into an ethnic conflict involving multiple armed groups, has killed tens of thousands of people in the world's youngest nation, which gained independence from Sudan in 2011. African Union Commission chief Nkosazana Dlamini-Zuma this week warned the nation was facing a "catastrophic humanitarian situation" with the "loss of countless human lives and untold suffering."