Aid operations need urgent funding in north Africa's Sahel region where five million children face the prospect of acute malnutrition, UN humanitarian agency OCHA said. "We are facing a funding bottleneck at a very critical moment. The planting season is only a couple of months away," said UN Assistant Secretary General Robert Piper. This year 20 million people in the region face food insecurity, and "five million children are projected to suffer from acute malnutrition," the UN  Office for the Coordination of Humanitarian Affairs said in a statement. "If humanitarian operations are delayed or have to scale down, the full impact will be felt in a couple of months --  and the most vulnerable families will be the first to suffer," said Piper. Sahel countries, which include land-locked Chad, Mali and Niger, are among the most isolated areas of the world. "Access is often challenging and delivering aid takes time," said Piper. Mali descended into chaos when Tuareg rebels and Islamist groups took over the north after a military coup in March 2012 far to the south in the capital Bamako. The Islamists later routed the Tuareg, who made a comeback following a French intervention. A humanitarian crisis sparked by the conflict came on top of years of drought in the Sahel region, with 800,000 Malians relying on food aid. "We need funding today to ensure that a child in a remote village can be treated against severe malnutrition in July," said Piper. A three-year plan for the Sahel aims to help more than 15 million people in Burkina Faso, Cameroon, Chad, Gambia, Mali, Mauritania, Niger, Nigeria and Senegal. Since its launch in February, the plan has received only 19 per cent of the required $2 billion funding for this year alone, OCHA said.