Two young Sudanese women appear to have suffocated to death on Sunday while trying to reach Britain from northern France in a small boat crammed with more than 80 people, including pregnant women and children, officials said.

This was the third such tragedy in just over a month.

The women, aged around 20, were aboard a small boat carrying 82 people that set out to sea south of the town of Neufchatel-Hardelot, Christophe Marx, a local government official, told reporters. Officials believe the two victims are of Sudanese origin.

Separately, Utopia 56, a migrant aid association, described the two victims as a 16-year-old child and a 20-year-old woman. One other victim - a pregnant woman -- was in critical condition, the group said.

"We can't see the end of this story. No one has the real solutions. And it's tragic," Paulette Juilien-Peuvion, the mayor of Neufchatel-Hardelot, told AFP.

She said she was sad to see "these young people trying to flee."

"There were notably pregnant mothers among them. I heard about a pregnant mother who also had another child with her," she said.

The boat set out to sea south of Neufchatel-Hardelot, about 12 kilometres (seven miles) south of Boulogne-sur-Mer, during the night from Saturday to Sunday.

But "the engine wouldn't start," and the boat began to drift, Marx said.