The actress disappeared on March 1 and her headless torso was discovered in the Regents Canal in Hackney on Tuesday (March 6).
Police confirmed yesterday that the body had been formally identified as the 29-year-old's. A 35-year-old man, thought to be McCluskie's brother, remains in custody following his arrest in connection with the case.
Dean Gaffney wrote: "RIP Gemma. Words can not (sic) explain how sad this is, what a cruel world this can sometimes be. My thoughts and prayers go out to your loved ones X."
Brooke Kinsella, whose brother Ben was murdered in 2008, said: "Thinking of you Gemma. I am so so sorry. Despair of the world we live in sometimes. RIP darling xxx."
Joe Swash added: "Thats (sic) two young amazing people I know with so much talent who have been killed in the last few years! Ben kinsella and now Gemma! RIP xxxx."
Meanwhile, an EastEnders spokesperson today told Digital Spy: "We are extremely saddened to hear the devastating news about Gemma McCluskie. Our thoughts are with her family and friends at this difficult time."
McCluskie played Kerry Skinner in EastEnders, a close friend of Zoe Slater and the great-niece of Ethel Skinner. The character also dated Robbie Jackson (Gaffney), who proposed to her at one stage.