Tribesmen shout slogans as they attend a gathering held to show support to the armed Houthi militias in Sanaa, Yemen December 6, 2016.

Yemen’s warring parties are refusing to discuss UN-brokered peace efforts, the United Nations’ envoy for the country said on Tuesday, amid an escalation in violence that he said was having a “dramatic” impact on the civilian population.

Already desperately poor even before the war, Yemen is now in the throes of a major humanitarian crisis.

“We know today that a solution is close because we know it. We know that a solution in Yemen will be based on a military and political aspect so it’s a bit of a shame that the parties don’t want to sit down at the table to discuss that,” UN envoy Ismail Ould Cheikh Ahmed told reporters after talks in Paris with French Foreign Minister Jean-Marc Ayrault.

“One of the subjects that concerns us the fact that we’re seeing an increase in military operations with the consequences which that is having on the civilian population,” Ahmed said.

While government forces in the south and east nominally hold most of Yemen’s territory, President Abd-Rabbu Mansour Hadi has struggled to enforce state authority among various militias, militants and tribes.

The Houthi militia controls most of Yemen’s population centers in the northwest, including Sanaa. Army forces and a group of militias called the Southern Resistance launched an offensive on the Red Sea coast this month to deprive the Houthis of ports and to isolate them in the inland capital.

Some 7.3 million Yemenis are now classed by the UN as “severely food insecure,” while there has been an upsurge in civilian casualties as bombing and fighting intensify.

“This is a conflict that is less talked about than others, but it can’t be forgotten because the humanitarian consequences on the ground are catastrophic,” said France’s Ayrault.