Another senior official, Major-General Hussein Kamal, said the government was "trying to investigate and confirm the report" that al-Masri had been killed in a battle within his own group.
The internet statement by the Islamic State in Iraq "assures the Islamic nation about the safety of Sheikh Abu Hamza al-Muhajir, may God save him, and that he is still fighting the enemies".
Tribe claims credit
Late on Tuesday, the leader of a Sunni Arab group opposed to al-Qaeda told Iraqi television that his fighters tracked down and killed al-Masri along with seven of his aides, two of them Saudis.
"Eyewitnesses confirmed his death and their corpses are still at the scene," Abdul-Sattar al-Rishawi, head of the Anbar Salvation Council, said.
Another member of the Anbar Salvation Council, an alliance of Iraqi tribes that are opposed to al-Qaeda's presence in the Iraqi insurgency, told the AFP news agency that al-Masri had been killed by members of the al-Dulaimi tribe.
"The clashes started between the Dulaimi tribe, which is part of the Salvation Council, and Al-Qaeda at 9am (05:00 GMT) and continued until 11," Sheikh Hamid al-Hayis, head of the Anbar Salvation Council, said.
"They killed him along with two Saudi leaders and three Iraqis."
Iraq's interior ministry said on Tuesday it had received intelligence information on al-Masri's apparent death, and that Iraqi security forces were not involved.
"Some information ... needs confirmation, but this information is very strong," said Brigadier-General Abdel Karim Khalaf, interior ministry operations director.
"The clashes took place among themselves. There were clashes within the groups of al-Qaeda. He was liquidated by them."
Khalaf said that al-Masri was apparently killed in a battle near a bridge in the town of al-Nibayi, north of Baghdad.
He said that Iraqi authorities did not have al-Masri's body.
A US military spokesman could not confirm the report, and said that several previous reports of al-Masri's death were found to be false.
"I hope it's true, we're checking, but we're going to be doubly sure before we can confirm anything," Lieutenant-Colonel Chris Garver said.
In March, Iraqi media reported that al-Masri had been wounded in a shootout with Iraqi soldiers, but the information proved unfounded.
US officials have said al-Masri is an Egyptian who specialises in car bombings.
He has allegedly headed al-Qaeda's operations in Iraq since the death of then-leader Abu Musab al-Zarqawi in a US air-raid in June 2006.