Britain has condemned the decision of President Robert Mugabe to ban all aid agency field work in Zimbabwe.
A spokesman for Prime Minister Gordon Brown described the plight of the country as a "tragedy".
"We utterly condemn the behaviour of the Zimbabwe regime," the spokesman said. "Obviously it is a tragedy that a country that could feed its people and export the excess is dependent on food aid in this way and has taken steps to remove access to food aid to its citizens."
The move to ban international aid agencies, announced on Thursday night in Harare, comes amid signs of a new security crackdown in Zimbabwe ahead of the the run-off later this month in the disputed presidential elections.
On Thursday a party of British and American diplomats was detained at a roadblock by what was described as an "armed mob" of police, troops and so-called "war veterans" loyal to Mr Mugabe.
A Zimbabwean driver employed locally by the US embassy was beaten up while one of the American vehicles had its tyres slashed and the occupants were threatened with being burnt alive.
At the same time Mr Mugabe's rival for the presidency, opposition leader Morgan Tsvangirai, was detained for nine hours at a police station in Bulawayo, Zimbabwe's second city.
Western diplomats fear it is all part of an orchestrated campaign of intimidation designed to ensure victory for Mr Mugabe in the poll on June 27.
Aid agencies warned it was ordinary Zimbabweans who would pay the price for the decision to prevent them operating.
Save the Children spokesman Dominic Nutt said: "Save the Children is seriously concerned about the consequences relating to reports of the suspension of aid operations in Zimbabwe, particularly for the most vulnerable children who we work with and who need our help."
