A court in the Gaza Strip on Sunday sentenced three men to death over the assassination of a Hamas military commander that the Islamist movement accused Israel of masterminding.
After a trial that lasted four days, two of the accused were sentenced to be hanged and one to be shot, the military court announced.
The assassination of Mazen Faqha in the middle of the Hamas-run Gaza Strip on March 24 shocked the Islamist movement and raised the possibility of a new round of violence with Israel.
Hamas immediately blamed its arch-enemy, with which it has fought three wars since 2008, and implemented strict border restrictions on those seeking to leave the Palestinian enclave.
Israel has not confirmed or denied the accusations.
In Sunday's court ruling, the chief suspect, Ashraf Abu Leila, 38, was sentenced to hang after being convicted of murder.
Hisham al-Aloul, 44, was also sentenced to hang, and Abdallah al-Nashar, 38 and who had been a member of Palestinian president Mahmud Abbas's presidential guard, will face the firing squad. They were convicted of collaborating with Israel.
Al-Aloul had entered the court yelling pro-Hamas slogans such as "long live the resistance".
The verdict was announced by the head of the military court, Nasser Suleiman, with none of the accused's relatives present.
They were led away by security forces as onlookers gathered to watch.
The verdicts cannot be appealed.
Faqha, 38, had been in charge of forming cells for Hamas's military wing in the occupied West Bank.
He had spent years in an Israeli jail before being released as part of a 2011 prisoner exchange deal.
After the arrest of the main suspect, Hamas leader Ismail Haniya pledged that "punishment will be carried out against the murderer".
Last week, Hamas released what it said was a recording of the confessions of the accused.
Images allegedly showed three men, presented as the murderer and his two accomplices, confessing to their roles, although their faces did not appear.
No independent bodies had access to the suspects, and the images and recordings were impossible to verify.
"Widespread coercion, torture and routine deprivation of detainees' rights by Hamas security services in Gaza call into question whether these confessions were in fact voluntary or may have been extracted under duress," Omar Shakir, Human Rights Watch director for Israel and the Palestinian territories, said last week.
Shortly after Faqha's killing, the security services launched a campaign against so-called collaborators.
On April 6, Hamas hanged three men accused of collaborating with Israel in cases unrelated to Faqha's death.
Executions in the Gaza Strip have drawn intense international criticism, though Hamas has pressed ahead.
Hamas says Faqha played an important role in major assaults, including a suicide attack in the Israeli settlement neighbourhood of Gilo in east Jerusalem in 2002 that killed 19 people.
They were part of a wave of suicide attacks that killed hundreds of Israelis during the second intifada, or uprising, between 2000 and 2005.
Israel sentenced him to nine life sentences plus 50 years, but he was released in a 2011 deal for Gilad Shalit, an Israeli soldier Hamas had held for five years.