Somalia's al-Shabab militants have banned the International Committee of the Red Cross (ICRC) from operating in parts of the country it controls.
The Islamist group said the ICRC had falsely accused them of blocking aid and had been handing out unfit food.
Al-Shabab controls large parts of south and central Somalia, which is suffering its worst drought in decades.
The ICRC, one of the few aid agencies operating there, said it had not heard about the ban.
The agency had suspended food distribution earlier this month saying militants had blocked supply routes, but it was still providing emergency care and water programmes.
Al-Shabab had already halted the work of several aid agencies working in the famine-hit region, including some from the UN. It accused them of exaggerating the scale of the problems for political reasons, and trying to convert Muslims to Christianity.
In a statement, it said the ICRC had "repeatedly betrayed the trust conferred on it by the local population and, in recent weeks, falsely accused the mujahideen [al-Shabab fighters] of hindering food distribution".
The group said 70% of food it had inspected in ICRC warehouses was unfit for human consumption, and that it had since destroyed nearly 2,000 tonnes of "expired" rations.
Somalia is said to be one of the world's most dangerous places for aid workers to operate. It has not had a functioning central government for more than 20 years and has been wracked by fighting between various militias.
The UN-backed government runs only a few areas, including the capital, Mogadishu, which al-Shabab withdrew from in August.
The UN says the areas worst affected by famine are in the southern and central areas, which are under the control of the al-Qaeda linked group.
In recent weeks, al-Shabab has lost ground to both Kenyan and Ethiopian forces, which have moved onto Somali territory.