Traffic along the Channel Tunnel has been disrupted overnight after migrants tried to enter the terminal in Calais.

"From 10.30pm (local time), around 150 migrants attempted to enter the platforms," an official for the Pas-de-Calais prefecture said.

The spokesman said traffic was interrupted with long queues of lorries and cars forming, but it was reported to have resumed a few hours later.

Eurotunnel said its service was suffering delays overnight due to what was described as an "incident on the terminal" at Calais.

A statement on the firm's website said: "For customers travelling today via our UK terminal, our passenger service is currently operating to schedule with up to four departures per hour.

Meanwhile, English police in Kent this morning implemented phase two of Operation Stack - where lorries heading for Dover are queued on parts of the M20 to ease congestion on local roads when there is disruption at the tunnel.

Ferry services are operating as normal at the Port of Dover, police said.

It is unclear whether the latest disruption is related to industrial action by French workers which caused delays earlier this week.

Lorry drivers faced days of misery as they were held in miles of queues until Operation Stack was lifted yesterday evening.

More than 3,000 hauliers were parked on the M20 after the closure of the Port of Calais earlier this week crippled Channel sailings.

The chaos was sparked after MyFerryLink workers began a strike on Monday in protest at expected job cuts.

Around 3,000 migrants are currently camped out around Calais and are trying to cross the Channel into Britain.

France and Britain signed an agreement last September, creating a fund of €5m per year to help Calais cope with the influx of migrants by reinforcing security around the port and the Channel Tunnel entrance.