The 'Poker Face' hitmaker is said to be terrified of being murdered by a crazed fan in a similar way to Beatles legend John Lennon ' who was shot dead on the steps of his apartment building in 1980 - and has boosted security to be with her at all times, even moving some staff into her New York apartment.

A source said: Gaga thinks some of the fan mail has been pretty ominous. Some of her fans are completely obsessed ' they make weird comments like saying they won't be happy until they die with her.

'She worries over how John Lennon died and fears the same happening to her. She has these horrible thoughts that there may be plans to kill her.

'Her security team are always close by. She is becoming more and more reliant on them and won't go anywhere alone. Her bodyguard even sits in her room as she sleeps.'

However, the singer's boyfriend Luc Carl is said to be unimpressed by the constant security presence.

The source added to heat magazine: 'Luc is getting a bit sick of having security around all the time. When they're hanging out at Gaga's place and her bodyguard is there, it kills the mood. But if she feels safer, he understands.'