Strictly bosses last night put the set on lockdown after death threats were sent to stars, reports claim.
A source at the show said ex-military personnel were brought in to surround the BBC studio last night ahead of the first live show.
An insider told The Sun a new protection team were sent in after “a couple of specific, very sinister threats”.
Contestants were reportedly assigned codenames during a secret security briefing.
Security on the set was beefed up in the wake of the sickening letters, which allegedly included death threats to stars such as Alex Scott and new judge Motsi Mabuse.
Stars on the show have also reportedly been banned from posting photos from their training sessions, in case the venues are identified.
They have also been advised to have their homes guarded while they are on TV.
Security now has a hotline to police in case of an emergency.
The source added: “Each year celebs get letters but this year there have been a few stand-out, deeply sinister ones which were flagged to the in-house team.”
They explained that “an external company” including “ex-military personnel” were now in place, and security teams had “weekly briefings” ahead of the live show.
Plain-clothed security staff were reportedly seen in place outside Elstree Studios, Herts, where the show is recorded.
Celebs Saffron Barker and Kelvin Fletcher, as well as pro-dancers Katya Jones and AJ Pritchard, were seen leaving their hotel on Friday ahead of performing.
It comes less than three weeks after dancer Giovanni Pernice was temporarily blinded with pepper spray by robbers.
Another dancer, Pasha Kovalev was mugged for his phone back in June.
AJ Pritchard was beaten up last year in a sickening attack.
But the stars are said to be upbeat despite the increased security presence, with insiders claiming it has brought them “closer together”.
In a statement, the BBC said: “We have extensive security measures in place to protect cast, crew and audience, and arrangements are reviewed on a regular basis.”