New evidence of babies starving to death in Yemen has emerged as the United Nations (UN) and aid agencies issue urgent calls for increased aid deliveries to feed 7 million people at risk of famine.

Key points: Children are so hungry they don't have energy to cry, Save the Children says

Children are so hungry they don't have energy to cry, Save the Children says Saudi Arabia, its allies prevent delivery of food and aid by sea, it says

Saudi Arabia, its allies prevent delivery of food and aid by sea, it says It calls on governments to put pressure on Saudi-led Coalition to unsure food aid

Charity Save the Children took the images this week in the Yemeni Capital Sanaa, in the wards of the Al Sabeen Hospital.

The NGO says its teams are seeing skeletal children in Yemen's hospitals on the brink of death, so hungry they do not even have the energy to cry.

"We are helping pregnant women who have starved themselves to feed their families, forced to choose between the living and the unborn," said Grant Pritchard, interim country director for Save the Children in Yemen.

"We are treating babies who have been sick since birth with diseases that are preventable and easily curable with the right medicines."

Forces loyal to the pro-Saudi President have been locked in an increasingly bitter war with Houthi rebel forces, who have conducted a decade-long campaign against the Government.

The conflict has devastated Yemen, collapsing the country's fragile economy and destroying critical infrastructure.

The NGO is calling on governments to put pressure on the Saudi-led Coalition to immediately ensure urgent food aid can be delivered through Yemen's main port on the Red Sea at Hudaydah.

Ships have recently been prevented from docking at the port due to bombed infrastructure and "security reasons" imposed by the Saudi Coalition.

"Right now the odds are stacked against us. We have had three shipments of life-saving medical aid delayed by the coalition so far this year, and our field teams tell us children have died as a result," Mr Pritchard said.

"By bombing and blocking Yemen's main port — the country's lifeline for essential supplies — Saudi Arabia and its coalition allies are preventing the delivery of food and aid by sea.

Currently, the Australian Government give no direct aid funding to Yemen. ( Supplied: Save the Children )

"This crisis is not an act of nature. It is man-made. Food and aid are being used as weapons of war."

Currently, the Australian Government gives no direct aid funding to Yemen despite the fact it has been classified as the world's worst humanitarian disaster.

Aid agencies have called on the Turnbull Government to immediately allocate aid funds to the country.

Yemen is one of four current famine or near-famine situations, along with South Sudan, northeast Nigeria and Somalia.

Last month the UN said more than $5 billion was needed by the end of March to prevent more than 20 million people in the four at-risk countries starving in the next six months.