North Koreans are forced to pay bribes to officials to survive in their isolated country, where corruption is "endemic" and repression rife, the United Nations human rights office said on Tuesday.

Officials across North Korea extort money from a population struggling to make ends meet, threatening them with detention and prosecution - particularly those working in the informal economy, it said in a report.

There was no immediate comment by Pyongyang, which was sent the U.N. report hours before publication.

North Korea blames the dire humanitarian situation on U.N. sanctions imposed for its nuclear and ballistic missile programmes since 2006. But the report said that the military receives priority funding amid "economic mismanagement".

"I am concerned that the constant focus on the nuclear issue continues to divert attention from the terrible state of human rights for many millions of North Koreans," Michelle Bachelet, U.N. High Commissioner for Human Rights, said in a statement.

"The rights to food, health, shelter, work, freedom of movement and liberty are universal and inalienable, but in North Korea they depend primarily on the ability of individuals to bribe State officials," she said.

Four in 10 North Koreans, or 10.1 million people, are chronically short of food and further cuts to already minimal rations are expected after the worst harvest in a decade, a U.N. assessment said earlier this month.

"The threat of arrest, detention and prosecution provide State officials with a powerful means of extorting money from a population struggling to survive," the U.N. rights office report said.

Bribery is "an everyday feature of people's struggle to make ends meet", said the report, entitled "The price is rights". It denounced what it called a "vicious cycle of deprivation, corruption and repression".

It is based on 214 interviews with North Korean "escapees", mainly from the northeastern provinces of Ryanggang and North Hamgyong, bordering China. They were the first to be cut from the public distribution system that collapsed in 1994, leading to a famine estimated to have killed up to 1 million, it said.

"If you just follow instructions coming from the State, you starve to death," a woman from Ryanggang, now living in South Korea, was quoted as saying.

CASH OR CIGARETTES

"If you have money you can get away with anything, including murder," another unnamed North Korean defector testified.

Many North Koreans pay bribes of cash or cigarettes not to have to report to state-assigned jobs where they receive no salary, thus allowing them to earn income in rudimentary markets, the report said.

Others bribe border guards to cross into China, where women are vulnerable to trafficking into forced marriages or the sex trade, it added.

Bachelet urged North Korean authorities to stop prosecuting people for engaging in legitimate market activity and to allow them freedom of movement within the country and abroad. China should not forcibly repatriate North Koreans, she added.

The United States called on North Korea this month to "dismantle all political prison camps" and release all political prisoners, who it said numbered between 80,000 and 120,000.