Survivors of an alleged gas attack in Syria have described their devastation after losing 22 relatives including women and children in the blast.

The Alyousef family was among the heaviest hit by the blast in Idlib early on Tuesday morning. Among them was a father whose wife and nine-month-old twins were killed.

Another relative, Abdul-Majid Alyousef, described his grief as he comes to terms with the devastation to his family from the attack, which left at least 86 people dead including 30 children.

Sarin, it was a hit at 7am in the morning. Women and children. There are wounded and missing, about 400. Now, people are in shock. Deaths are many. The Alyousef family, 22 were buried so far. My family, 22. The wounded and in hospitals are about 70, and 50 people are missing, women and children from Alyousef family in Khan Sheikhoun.

Abdul-Majid Alyousef
'People thought it was a regular aerial bombardment.' Credit: APTN

Another member of the family, Mehmet Abdul Moein Alyousef, 19, said he was aware of 20 deaths among his relatives.

"Everyone was sleeping, there was no one on the streets," he said.

"People thought it was a regular aerial bombardment. They went to where the plane hit and saw that it was a chemical gas and that's when they were affected by it."

He added that his uncle was among those being treated.

"When he came here he couldn't see. His mind wasn't all there because of the chemical gas. Thank God he has come to and he's talking a little," he said.

Officials have said at least 30 children were among the victims of the attack on Tuesday, with Turkey reporting that initial tests suggest that Syrian government forces used the banned nerve agent Satin in the bombardment.

Both Syria and its key ally Russia have denied that nerve agent was used by state forces.