Kevin McGuigan Sr , 53, was shot dead at his home at Comber Court in the Short Strand on Wednesday.
A police spokesman said a 44-year-old man and a 39-year-old woman were arrested "as part of the overall investigation".
A number of searches have also been carried out.
Mr McGuigan, a father-of-nine, was taken to the Royal Victoria Hospital but died a short time later.
Police believe two men shot him several times in the head and chest at point blank range before running off.
Police investigating the murder of a former Provisional IRA member have arrested two people in east Belfast.