Jan 11 (Reuters) - In a nation where opposition to almost half a century of clerical rule has long been fragmented, the son of the last shah of Iran has become a prominent voice spurring on protesters staging the biggest anti-government demonstrations in years.

Reza Pahlavi, 65, has sought to speak as a national leader despite living outside Iran since before his father was toppled in the 1979 Islamic Revolution.

By Parisa Hafezi, Rami Ayyub and Maayan Lubell

DUBAI/JERUSALEM, Jan 11 (Reuters) - Tehran threatened on Sunday to retaliate against Israel and U.S. military bases in the event of U.S. strikes on Iran, issuing the warning as Israeli sources said Israel was on high alert for the possibility of any U.S. intervention.

At a hospital in Gaza, wards are filled with patients fearing they will be left without care if Doctors Without Borders (MSF) is forced out under an Israeli ban due to take effect in March.

Last month, Israel announced it would prevent 37 aid organisations, including MSF, from operating in Gaza from March 1 for failing to provide detailed information on their Palestinian staff.

"They stood by us throughout the war," said 10-year-old Adam Asfour, his left arm pinned with metal rods after he was wounded by shrapnel in a bombing in September.

Iranians took to the streets in new protests against the clerical authorities overnight despite an internet shutdown, as rights groups warned on Sunday that authorities were committing a "massacre" to quell the demonstrations.

The protests, initially sparked by anger over the rising cost of living, have now become a movement against the theocratic government that has ruled Iran since the 1979 revolution and have already lasted two weeks.

Jan 11 (Reuters) - Israel is on high alert for the possibility of any U.S. intervention in Iran as authorities there confront the biggest anti-government protests in years, according to three Israeli sources with knowledge of the matter.

President Donald Trump has repeatedly threatened to intervene in recent days and warned Iran’s rulers against using force against demonstrators. On Saturday, Trump said the U.S. stands “ready to help”.

WASHINGTON, Jan 10 (Reuters) - U.S. Secretary of State Marco Rubio spoke over the phone with Israeli Prime Minister Benjamin Netanyahu on Saturday, Axios reporter Barak Ravid said on X, adding they discussed protests in Iran along with Gaza and Syria.

Ravid cited a U.S. source.

(Reporting by Kanishka Singh in Washington; Editing by Andrea Ricci)

Jan 11 (Reuters) - The last Kurdish-led Syrian Democratic Forces fighters have left Aleppo, Syrian state-run Ekhbariya TV said on Sunday.

The SDF head said the group had reached an understanding on a ceasefire and the evacuation of trapped civilians and fighters from Aleppo's Ashrafiyya and Sheikh Maksoud neighborhoods to northern and eastern Syria.

(Reporting by Yomna EhabEditing by Rod Nickel)

By Kanishka Singh

WASHINGTON, Jan 10 (Reuters) - Bangladesh said on Saturday it has told the United States that it wants to join the international stabilization force that would be deployed in Gaza.

Bangladesh said its national security adviser, Khalilur Rahman, met U.S. diplomats Allison Hooker and Paul Kapur in Washington.

A protester briefly replaced the flag of the Islamic Republic of Iran on its London embassy with a former flag, flown before 1979, during a demonstration Saturday, witnesses told AFP.

A video posted to social media showed a man on the balcony of the embassy, near Hyde Park, replace the country's current flag with one used during the rule of the ousted shah to cheers from hundreds of demonstrators below.

The flag -- tri-coloured, with a lion and sun, surrounded by a wreath and crown -- was a ceremonial one used in Iran before the Islamic revolution.

Jan 10 - Egypt’s National Elections Authority declared the results on Saturday of the last 49 seats in a parliamentary election that began more than three months ago and gave President Abdel Fattah al-Sisi the super-majority he needs to amend the constitution.

The results of the final seats had been held up by reruns of voting in constituencies where initial results had been annulled.