Intrigue as armed police seen 'boarding huge cargo ship on Thames in SBS-style operation'

EXCLUSIVE: THE public have been warned not to be alarmed if they see armed police boarding large boats on the River Thames after an unannounced training exercise sparked concern.

Members of the public feared something terror related or a major immigration raid when four police boats were seen heading towards a huge cargo ship in the river near Dagenham, east London, on Thursday, August 17.

Similar, but smaller scale operations have since been spotted on Thursday, August 24 and Thursday, August 31.

A witness said of the August 17 event: "There were two normal police boats and two inflatables, all marked police, which came out to the ship. It was at a distance, but armed officers boarded the ship, so there was definitely something going on. It was like a special boat service raid on the ship, but then it was escorted down the river (towards the estuary) by police boats.

"Someone who works nearby said that they were looking for Illegal immigrants, but it was just a rumour."

Watch the video above of officers boarding on August 17 and below of the exercise on August 31.

Essex Police, National Crime Agency, Home Office and Ministry of Defence denied any knowledge of the incident involving the Wilhelmine, which flies under the flag of Malta, and was bound for the Netherlands, on Thursday, August 17, at about 11am.

Adding to the mystery the Met Police initially said it may be a training exercise, but later also said that it was not involved.

However, after further checks, the Met Police confirmed it had been an unannounced training exercise.

A spokeswoman said: "It was a training exercise."

She said there would be more "over the coming weeks" in case people were to spot similar activity.

However, the force refused to divulge what form of training exercises were taking place and whether it was terror or border security related.

The spokeswoman added: "We are not providing a running commentary on the training."

CLDN Ports London, which operates the Wilhelmine, did not respond to a request for comment.