Sinwar, Hamas' political leader believed to be hiding underground in Gaza, told Nasrallah that the group was committed to the line of resistance followed by its predecessor Ismail Haniyeh, who was assassinated by Israel.

The letter, shared on Hezbollah's Telegram channel, was written to express gratitude for Hezbollah's ongoing war against Israel, which began on October 8, just one day after Hamas attacked Israel, leading to Israel's devastating war in Gaza.

One of Israel's most wanted men, Sinwar had not been seen since the outbreak of hostilities. Nor had he been heard from publicly for nearly a year - until this week.

On Tuesday, Sinwar also made his first statement since the war, congratulating Algerian President Abdelmadjid Tebboune on his election victory, according to Hamas' Telegram channel.

The next day, his office said he had written a letter thanking those who had expressed condolences over Haniyeh's death. And on Friday, the letter was sent to Nasrallah.

Sinwar was appointed Hamas' political leader after Haniyeh was assassinated in the Iranian capital Tehran last July. He is seen as more hardline than his predecessor on relations with Israel and favors closer cooperation and ties with Iran and allied Islamist groups such as Hezbollah.

Muhammad Shehada, a Gaza-based analyst, said Sinwar was “one of the strongest advocates for closer ties with Hezbollah and Iran, as well as a strengthening alliance with the ‘Axis of Resistance.’ He is seen as a pragmatist within the movement, but at the same time very unpredictable and impulsive.”

In a letter to Nasrallah, Sinwar vowed to continue protecting Islam's holy sites, especially the Al Aqsa Mosque in Jerusalem “until the occupation is expelled and removed from our country, and an independent state with full sovereignty and Jerusalem as its capital is established.”

Bui Huy (according to AP, CNN)