A hate crime investigation has been launched by a counter terrorism unit after a threatening letter was sent to a mosque.

The abusive letter was sent to Southend Mosque and coincided with a number of similar incidents across the country, including a mosque in Colchester and three mosques in Kent.

Mosques in Blackpool, Maidstone and Canterbury were cordoned off after the letters were discovered to contain a white powder which was later found to be harmless.

No injuries were reported.

The exact nature of the letter sent to the mosque in Southend is not known but it did not contain any suspicious substance.

The horrific hate mail sent to a mosque in Colchester described Muslims as “filthy, subhuman vermin”.

The author said he had a weapon and he was happy to use it on members of the mosque.

It is feared the sentiments in the letter to the Southend religious building on May 3 were similar.

The author of at least one of the letters stated his aim, for Punish a Muslim Day, didn’t go as expected but said there was still time.

In March this year, several MPs including Sajid Javid were sent abusive letters which offered “rewards” for those who attack and abuse Muslims on a single day of coordinated nationwide violence.

Essex Police confirmed the incident in Southend is being investigated as a hate crime but they are no longer leading the probe.

The investigation is being lead by the Counter Terrorism Unit North East based in Leeds.

A spokesman for the CTU said: “Police are investigating a number of reports of malicious communications sent to individuals across the UK.

“Officers are currently investigating the full circumstances surrounding these reports.

“Counter Terrorism Policing North East are coordinating the investigation at this time and will consider any potential links to existing enquiries.

“Enquiries are at an early stage and we’d encourage anyone who believes they have been a victim of such an offence to contact their local police force.

"We’d also appeal to anyone with any information about the individual, or individuals, responsible to call police in confidence on 0800 789 321.”

There are now 39 hate incident reporting centres across the county and 450 people from the public and voluntary sector.

The team have been fully trained as hate crime ambassadors, which Essex Police say allows them to build on their commitment to tackle hate crime and support victims.

If you do not have the confidence to talk to the police you can report it to centres by visiting www.essex.police.uk/advice/hate-crime/#hircs or visit www.report-it.org.uk.

You can also report crime anonymously to Crimestoppers on 0800 555 111.