A knife-wielding man wearing a “Phantom of the Opera” mask and a wig allegedly stabbed to death his ex-girlfriend before slitting his own throat.

The 23-year-old victim died after being attacked last night while at work as a receptionist at St. George’s International College in Plaistow, east London.

A second woman, believed to be her colleague, was stabbed in the shoulder in the incident.

A 29-year-old man was under police guard in the hospital Tuesday after being arrested on suspicion of murder and attempted murder.

Detectives confirmed that the suspect was seen immediately before the attack wearing a curly black wig and a Phantom of the Opera-style face mask.

Taxi driver Ken Bristow reported seeing a witness run from the college yesterday evening, screaming: “He’s killing her.”

The suspect then “slit his own throat” as he grappled with police officers, he said.

Mr Bristow added: “I was told she must have been stabbed dozens of times. There was blood everywhere.

“After police and ambulances arrived, the attacker was taken away. He had been wearing a mask and cloak.”

Locals said the suspect was a former boyfriend of the murder victim.

One man, who did not want to be named, said: “He went for her friend first, then he went for his ex-girlfriend.”

The victim has not been named but is thought to be from Dagenham, east London.

Police are expected to identify her officially after a post-mortem examination later today.

Officers are at the hospital bedside of the suspect under arrest and will transfer him to a police station when his condition improves.