An Emirati woman has been arrested over the fatal stabbing of an American teacher and a foiled plot to bomb the home of another US citizen, UAE authorities said Thursday.

Interior Minister Sheikh Saif Bin Zayed said the woman, believed to be the veiled suspect who killed the American woman Monday in a shopping centre toilet, had also attempted to plant a makeshift bomb in front of the home of an American doctor in Abu Dhabi.

The suspect "is in the hands of the police," the minister said.

Police said the suspect was a 38-year-old Emirati, who they have dubbed "The Reem Island Ghost" after the location of the shopping centre where Monday's attack took place.

"We are witnessing an unprecedented, heinous crime in the UAE," Saif said, threatening "deterrent punishment against whoever attempts to tamper with UAE security."

The United Arab Emirates hosts millions of foreigners and has remained largely unscathed as unrest swept other Arab countries.

In CCTV footage released on Wednesday, the assailant is seen entering the shopping mall shortly after 1:00 pm and then rushing from the restroom about 90 minutes later, as panicked shoppers scrambled.

The footage was accompanied by pictures of a bloodied kitchen knife and trails of blood on the floor of the restroom.

Complete footage released by the ministry on Thursday showed the fully covered woman entering a building in Abu Dhabi, pulling a wheeled luggage case, where she was allegedly hiding a bomb.

The bomb was planted at the door of one of the apartments in the building.

The footage then shows a raid on a house where the woman, dressed in pyjamas, was with a man, whom the police handcuffed.

The ministry did not give details on the fate of the man or say if he had a role in the attacks.

It showed several knives and bombmaking materials, as well as traces of blood on the steering wheel of the suspect's car.

Police said Wednesday that the divorced American woman, who worked at an Abu Dhabi kindergarten, was stabbed by a person wearing a black robe, black gloves and a niqab -- a Muslim veil that conceals the face except for the eyes.

They initially said the woman was 37 years old but on Thursday said she was 47.

The victim's 11-year-old twins were taken into police care until their father arrived from abroad.

The stabbing took place on the same day as a recording was released attributed to Abu Mohammed al-Adnani, the spokesman of the extremist Islamic State group, that urged Muslims to attack Westerners by any means, even if only to "spit on their faces".

The UAE in September joined the US-led coalition carrying out air strikes against IS in Iraq and Syria.