More than a million lives could be lost three years after last disaster as country suffers poor rains and internal strife

Famine is stalking Somalia after a year of poor rains and heavy fighting, with more than a million lives at risk and little sense of urgency from the international community, the top UN envoy to the country warned.

Three years ago food shortages killed 260,000 people.

Many of the warning signs ahead of that disaster have appeared again this year, including poor rainfall, large numbers of people fleeing their homes, and roads blocked by the extremist al-Shabaab group.

"In plain language we are concerned about the risk of a repetition of the famine of 2011," said Nicholas Kay, head of the UN mission in Somalia. More than a million people are just "one step below" famine, he said, already hungry and in danger of worse. "A mixture of climatic reasons, displacement of population, and active al-Shabaab tactics of preventing food reaching towns by road, that combination of circumstances means we could tip over into famine."

Another two million people are very vulnerable to crisis, only just able to feed themselves and their families at present, the UN has estimated. The death toll in 2011 was exacerbated by delays in mobilising help. This year the UN is trying to feed people already going hungry, and build up more emergency reserves, but is short of funds.

"Unfortunately the international response was a bit behind the curve in 2011," Kay said. "We are seeing indicators very similar to the indicators from 2011, and at the same time the funding available for humanitarian work is disastrously low."

A call for $1bn to cover food, education, shelter and healthcare for the country's most vulnerable people has only won promises of $313m. If there is a famine, needs will be even higher. Even now health experts estimate that there are more than 40,000 Somali children who have been so deprived of food that they will die without emergency treatment. More than 160,000 others are acutely malnourished.

Another famine would also jeopardise the fragile process of rebuilding Somalia. The government collapsed in the early 1990s and since then the country has been plagued by a number of problems from civil war to piracy and the rise of al-Qaida affiliate al-Shaabab. "When we look at Somalia we are on the brink of seeing a country recover from two decades of state failure," Kay said. "(Another famine) would absolutely undo a lot of the political and humanitarian gains."