Some 800 to 1,000 migrants tried Thursday to break into the Channel Tunnel near France's port city Calais in a desperate bid to reach Britain, local officials said.

"We noted the presence of 800 to 1,000 migrants" near the tunnel, a local official told AFP, as a police source described the number seeking to cross the Channel as "unprecedented" for a single day.

"As they approached the tunnel, several migrants tried hard to slow down the flow of traffic so they could climb into the trucks," the source said.

An AFP journalist at the scene saw some people climb on top of trucks heading towards Britain.

"Security forces were deployed... objects were being thrown at them, and they had to resort to using tear gas," police said in a statement.

Some 4,500 people fleeing war and poverty in Asia, the Middle East and Africa live in notoriously squalid conditions in a makeshift camp in Calais known as the "Jungle".

Earlier this month a 16-year-old Sudanese boy was hit by a van on a motorway close to the Channel Tunnel, becoming the 18th person to die trying to reach Britain from Calais since June.