The report says the official go-ahead for the attack was given at a Monday meeting between the IRGC and Hamas officials in Beirut.
It has been revealed that Iran helped Hamas plan its attack on Israel that killed at least 700 people.
The attack took place on Sunday October 8, was given the green light by Iranian security officials.
According to a Wall Street Journal report, Hamas plotted the air, land and sea invasions with help from officers of Iran's Islamic Revolutionary Guard Corps (IRGC).
The report says the official go-ahead for the attack was given at a Monday meeting between the IRGC and Hamas officials in Beirut.
Four other Iranian backed military groups were reported to be at the meeting, including members of Hamas and Hezbollah.
'We don't have any information at this time to corroborate this account,' an American official said in the report.
Iran helped plan Hamas land, sea and air attack on Israel that killed at least 700 people, new report claims
A senior Hamas official said in a statement that they acted alone. 'This is a Palestinian and Hamas decision,' he said, bur a European official and adviser to Syria gave the same accounts as others that this was planned out in concert.
The sources quoted claims that members of each group have met with a branch of the IRGC biweekly since at least August to plan out the attack.
Some in attendance include IRGC military leader Ismail Qaani, Hezbollah leader Hassan Nasrallah, Islamic Jihad leader Ziyad al-Nakhalah, and Saleh al-Arouri, Hamas’s military leader.
Hossein Amir-Abdollahian, Iran's foreign minister, has attended two of the meetings.
Qaani has been the figurehead of a movement to unite Iran's foreign proxies since at least April in an attempt to increase the IRGC's influence in the middle east region.
Iran was branded a ‘terrorist state’ by Israel on Sunday night and Israel’s prime minister Benjamin Netanyahu has vowed a ‘mighty vengeance’, promising to reduce parts of Gaza run by Hamas ‘into rubble’.
Lieutenant Colonel Jonathan Conricus, spokesman of the Israel Defense Forces (lDF) said: ‘Without Iran’s funding, weapons, training, guidance and political incitement, Hamas would not have the capability nor the capacity.’
He added: ‘This was a watershed moment, unprecedented in scale, severity, brutality and the sheer joy with which terrorists were butchering Israeli citizens.
The Israeli government formally declared war Sunday and gave the green light for 'significant military steps' to retaliate against Hamas for its surprise attack from the Gaza Strip.
As at press time at least 700 people have reportedly been killed in Israel, and more than 300 have been killed in Gaza as Israeli airstrikes hit the territory.