His comments on Thursday came a day after Abu Ein, who served as settlements minister for the Palestinian Authority, collapsed after being heavily gassed and reportedly assaulted by Israeli soldiers during a protest against the construction of new Jewish settlements in the West Bank village of Turmus Ayya.
He later died in Ramallah hospital.
Speaking during a visit to Bosnia and Herzegovina on Thursday, Hussein said: "Ziad Abu Ein fought against the occupation and was killed in cold blood."
Hussein also said during a visit to a Srebrenica genocide memorial that Israeli soldiers had caused Abu Ein's death by not allowing him medical treatment.
'Struggle against occupation'
He said: "There is a relentless genocide in Palestine and, in the recent attacks by Israel on Gaza, 2,200 Palestinians were killed while more than 11,000 people were wounded."
"Among the martyrs, there was Ziad Abu Ein who was killed yesterday. He struggled against the occupation and was killed cold blooded on Wednesday because they did not allow him to receive first aid."
Hussein said that, despite the numerous martyrs, the Palestinian people would never give up their struggle for freedom, dignity and the establishment of their own state within their country.
Hussein also visited Srebrenica-Potocari Memorial and Cemetery for the Victims of the 1995 Genocide where he met relatives of the victims.
Praying for the victims of the genocide at the memorial, he wished that what happened in Srebrenica would never be repeated.