"Based on religious law and our religion and what is stipulated in Palestinian law ... three men convicted of intentional murder were executed on Tuesday morning in accordance with a court order sentencing them to death by hanging after their conviction," the ministry statement said.
The three were not identified by name, the official Palestinian news agency Wafa said.
The Palestinian legal system permits the death penalty, requiring final approval from Palestinian President Mahmoud Abbas. However, since taking over the Gaza Strip in 2007, Hamas does not recognize Abbas' authority and, therefore, did not seek his consent, Wafa said.
In Gaza in April, Hamas executed three Palestinians, one suspected of collaborating with Israel and two for murder.