Iranian journalist Momahad Ahwaze has claimed on Twitter that Iran's Supreme Leader Ayatollah Ali Khamenei has transferred his powers to his son as concerns about his failing health have mounted and the country faces increased tensions with Israel and U.S.

Writing in Arabic, Ahwaze said Khamenei had handed power over to his son, Mojtaba Khamenei.

"Iranian President Hassan Rouhani was scheduled to meet on Friday with the Iranian Leader Khamenei, this meeting between [Khamenei] and President Rouhani was canceled due to the deterioration of Khamenei's health condition," Ahwaze wrote.

Ahwaze went on to say that the cause of the supreme leader's ill health was not known, assertions about the senior Khamenei which Newsweek has not been able to independently confirm, but suggested it could be due to prostate cancer. Ahwaze claimed Khamenei deteriorated overnight.

Ahwaze, widely followed on Twitter, earlier this year helped expose the extent of Iran's COVID-19 outbreak, even as authorities tried to downplay it.

Khamenei would be stepping down amid increased tensions between Iran and Israel following the killing of top Iranian nuclear scientist Mohsen Fakhrizadeh on November 27.

The political and religious leader has demonstrated signs of illness in the recent past and is rumored to have prostate cancer. But it would also be highly unusual for the supreme leader to transfer powers in this way.

Iranian officials blamed Israel for Fakhrizadeh's assassination and promised retribution. The Iranian Revolution Guards Corps (IRGC) warned of "severe revenge and punishment."

The U.S. and Israel are strong allies and the Trump administration has backed Israeli policy in the region in the past. President Donald Trump's decision to pull out pf a key nuclear deal with Iran also ramped up tensions in recent years.

Secretary of State Mike Pompeo visited Israel less than two weeks before Fahkrizadeh's death. Israel has not confirmed whether it was responsible for the killing of Fahrkrizadeh.

The scientist's death and the Iranian leaders' reaction to it appear to have exacerbated pre-existing political divisions in the regime. In particular, instability in the IRGC is seen as a potential threat to Israel as the group attempts to further its own goals amid a potentially changing political landscape.

Israel's National Security Council warned on Friday that the country's citizens and facilities abroad could be at risk following the assassination of Fakhrizadeh and Iran's stated intentions.

"In light of the recent threats from Iranian elements and in light of the past involvement of Iranian elements in terrorist attacks in various countries, there is concern that Iran will try to act in this way against Israeli targets," the council said in a statement.

"It's possible that part of the current wave of Islamist terror will reach targets identified with Israel or [with] Jewish communities," the statement went on, citing "synagogues, Kosher restaurants, and Jewish museums" as possible targets.