NAIROBI (Reuters) - South Sudan is hiking fees for humanitarians and blocking them from reaching hungry families, even as the oil-rich country appeals for nearly 2 billion dollars to help avert starvation amid a civil war, five aid groups told Reuters. The government and the United Nations announced on Wednesday that South Sudan needs $1.7 billion in aid next year to help 6 million people   half its population   cope with the effects of war, hunger and economic decline. But aid groups said bureaucracy, violence and rocketing government fees were stopping their work, despite a promise from President Salva Kiir to allow unhindered access after the United States threatened to pull support to the government in October. All the aid workers spoke on condition of anonymity, citing fear of expulsion from the country.  Alain Noudehou, the U.N. s top humanitarian official in the country, said the increased fees are a major concern.  [It] will take away from the resources we have to address the crisis,  Noudehou, humanitarian coordinator for the U.N. Mission in South Sudan (UNMISS), said on Wednesday.  Juba announced plans in March to charge each foreign aid worker $10,000 per annual permit but later dropped them. It revised the fees steeply upwards last month, however, requiring some foreign aid workers to pay $4,000 for a permit   16 times the old rate.  At least two aid groups have paid, they told Reuters on condition of anonymity.  Humanitarian Affairs Minister Hussein Mar Nyout said on Wednesday he had received many complaints over the new fees and restrictions on travel for some aid workers.   This is not in the spirit of the president and we are going to implement the order of the president,  he said in response to questions at a news conference.                 About one-third of South Sudan s 12 million population have fled their homes since the civil war began in 2013, two years after it won independence from Sudan. The United Nations describes the violence as ethnic cleansing. Earlier this year, pockets of the country plunged briefly into famine.  The economy has nosedived, there is hyperinflation, and the government is unable to pay civil servants and soldiers because oil production has collapsed and official corruption is rampant.      The confusion over permits delays aid, organizations said.    Nobody understands who is giving directives and who is supposed to implement,  said the head of one international aid group in South Sudan. He said customs have seized his organization s IT equipment, despite an import tax waiver for aid groups. Last week, a team of doctors said they were denied permission to travel outside the capital because they had not received work permits they had paid for.  Another aid group said it is unable to bring in foreign  medical staff to complete a government-approved project because authorities said even a consultant visiting South Sudan for a week had to pay $4,000 for a permit that takes months to obtain.  The first issue is the inherent absurdity and impracticality of the rules,  said an employee of the aid group.  The second is that laws are being tried inconsistently by four government agencies that are at loggerheads.  South Sudan expelled the Norwegian Refugee Council s country director last year, while some 28 aid workers have been killed this year, with nine shot dead in November alone, according to the United Nations.   UNMISS staff are exempt from the work permit requirement but the government has forced some contractors to pay, in violation of an agreement with the U.N., an UNMISS spokeswoman said.  Juba is not honoring a similar treaty exempting aid agencies receiving U.S. funding, a Western diplomat said. 