The Ministry of Defence has launched an investigation after a race hate email purporting to be from one of its departments was sent to a Birmingham mosque.
Worshippers at Ahl-e-Hadith mosque in Small Heath received the email just three hours after the London bomb attacks last Thursday.
The message, claiming to be from the BNP, declared "war" on Muslims throughout Britain.
The email appeared to have originated from an address set up to receive general inquiries to the MoD's catering division.
The message, timed at 12:29:19 on 7 July, stated: "Its now WAR on Muslims through out Britain" (sic). It then delivers two lines of crosses before signing off with the initials "BNP".
The address it appeared to be from is part of the official MoD website.
A spokesman for the Ahl-e-Hadith mosque on Green Lane, Small Heath, said: "We were concerned when it initially came because it was on the day of the attacks, and that it was from an MoD address - but we haven't had any direct problems so it is not something we are going to worry about.
"We don't know for definite who it is from. It says the BNP but it could be anybody. But the BNP's views represent those of only a tiny minority of people, we hope."
An MoD spokeswoman said preliminary investigations indicated the email was not sent from the Defence Logistics Organisation, but all email records from the address were being thoroughly checked. She said: "We're looking into this as a matter of urgency.
"It is very easy to spoof email addresses and our IT people are attempting to check and cross reference the IP address to determine where it came from. This is absolutely not something that we condone."
Simon Derby, West Midlands spokesman for the right-wing BNP, said confirming whether there were BNP supporters in the Army "would not do the Army or the BNP any favours", but he was aware BNP literature was sometimes circulated among soldiers.
"We will get ourselves into trouble if we reveal we have people in the Army," he said. "Naturally the Army is a place where people are patriotic and we know of BNP literature being read among the troops and they write in to us, but we would not reveal anything about contacts within the Armed Forces."
A spokeswoman for West Midlands Police said the email had been reported to them but as it did not constitute a direct threat, there was nothing they could do.
She said the force had received very few reports of such warnings to mosques and Islamic organisations in the region since the London bombings.
"However, anyone using this tragic event as an excuse to send hate mail in any form is warned that West Midlands Police will not tolerate this behaviour and will take robust action as necessary," she said.