Days after Hamas accused Israel of electrocuting and poisoning one of its commanders in his Dubai hotel room, Israel on Sunday claimed the man played a critical role in smuggling rockets from Iran to Palestinian militants in Gaza.

Though Israel has not acknowledged any role in the Jan. 20 killing of Mahmoud al-Mabhouh, it was one of several mysterious deaths of Arab militants attributed to Israel's Mossad spy agency over the years.

Relatives and Hamas officials said al-Mabhouh was electrocuted and poisoned, perhaps by having his face smothered with a poison-soaked cloth. Despite surviving what his family says were several earlier attempts on his life, he had traveled without bodyguards to avoid drawing attention.

Hamas, which blamed Israel and has vowed to avenge al-Mabhouh's death, released photos Sunday showing that however al-Mabhouh was killed, it was brutal enough to leave bruises and red splotches on his face and nose.

Hamas has been quiet about the reason for al-Mabhouh's travels, though a brother says he was on a mission for the militant group. One senior Hamas figure, Osama Hamdan, denied al-Mabhouh was on a special assignment or that he was planning to head on from Dubai to Iran.

Israeli defense officials said al-Mabhouh was key to smuggling Iranian arms to Gaza, in particular, rockets that could fly as far as Tel Aviv, some 40 miles to the north.

Several rockets fired from Gaza during last winter's Israel-Hamas war had hit cities as far as 25 miles (40 kilometers) away.

The officials said al-Mabhouh was also suspected in the kidnapping and killing of two Israeli soldiers in 1989. They spoke on condition of anonymity because they were discussing confidential intelligence assessments.

The Mossad does not comment on its operations, but many of the details resemble past strikes attributed to the spy agency.

One of the Mossad's most high-profile failures bore similarities: In 1997 its agents were caught poisoning the militant group's leader, Khaled Mashaal, in Jordan. Israel was forced to send an antidote that saved Mashaal's life and release Hamas' spiritual leader from an Israeli prison.

Israel's prime minister, Benjamin Netanyahu, was also the prime minister at the time. Today, Mashaal is Hamas' supreme leader.

Iran has long been suspected of supplying weapons to Hamas, which smuggles supplies in through hundreds of tunnels snaking under Gaza's sealed border with Egypt.

Iran has acknowledged bankrolling Hamas but has never admitted arming the militant group, which wrested control of Gaza in June 2007. Israel is convinced Tehran has become a main pipeline for arms to Gaza.

Middle Eastern intelligence officials say Iranians are using islands they seized in the 1970s from the United Arab Emirates in the Persian Gulf to load weapons sent to Hamas to avoid being tracked by the American spy satellites.

Moderate pro-Western governments in the region have been cooperating with U.S. intelligence — and indirectly with Israel — to crack down on Iranian arms shipments to Hamas, they said.

The efforts are not necessarily meant to help Israel. Arab countries are also concerned that Iranian weapons are reaching rebels in Yemen and Hezbollah guerrillas in Lebanon. Last November, Israel seized a ship that it said was carrying hundreds of tons of Iranian weapons to Hezbollah.

The precise circumstances of al-Mabhouh's death remain cloudy.

Hamas said al-Mabhouh was killed on Jan. 20. Relatives and Hamas officials said al-Mabhouh was electrocuted and may have had his face covered by a cloth soaked in poison.

Al-Mabhouh's brother, Hussein, who lives in Gaza, said he was told by Hamas officials that security cameras in the hotel filmed two suspects outside his hotel room. It was not clear whether the assailants could be identified.

"He was in Dubai for a mission," Hussein al-Mabhouh said. He said the slain Hamas leader, who lived in Syria with his family, frequently traveled to Dubai for the militant group, but did not say what he did there.

Hamas military spokesman Abu Obeida confirmed al-Mabhouh was passing through Dubai but did not say where he was headed.

Al-Mabhouh did not have bodyguards with him. The brother said al-Mabhouh did not like drawing attention to himself and often traveled without bodyguards.

His brother said he survived several assassination attempts, one in 1989, another two years ago in Beirut, where a poisoning attempt left him comatose for 36 hours. In neighboring Syria, a bomb was found under a car he was meant to enter.

Dubai authorities have said a "professional criminal gang" with European passports was likely behind the killing.

Earlier this month, Iran accused Israel of killing a nuclear scientist, and Hezbollah blames Israel for the assassination of a senior military commander in Damascus in 2008.

Last year, Sudan — a close ally of Iran and Hamas — accused Israel of attacking a convoy in a remote mountainous desert region of northeastern Sudan. Media reports said the attacks targeted convoys smuggling weapons en route to Gaza.

One ex-Mossad agent was skeptical, saying al-Mabhouh's killing was "not Israel's style." Ramy Igra told Israel TV, "al-Mabhouh was an arms dealer and was probably cutting corners on all sides, so its more likely that whoever settled the score was a financial partner."

Mahmoud Zahar, a top Hamas leader in Gaza, said Hamas would retaliate for the assassination, though it appears unlikely it is ready to end a yearlong lull that has prevailed since Israel ended a fierce offensive in the Hamas-ruled Gaza Strip last year.