By Jon Leyne
BBC News, Tehran
Iran is one of the strongest supporters of Hamas
Iran's official media paint a picture of a country in ferment, outraged by the Israeli attack on Gaza.
There are daily reports of demonstrations across the country by students and members of the Basij - the militia arm of the Revolutionary Guards.
Iranian MPs have volunteered to travel to Gaza to fight alongside Hamas.
One group of students occupied part of one of the British embassy compounds, unfurling pro-Palestinian banners.
Another group staged a sit-in at one of Tehran's airports, waiting, perhaps slightly optimistically, for a flight to the Gaza Strip.
Politicians and religious leaders have lined up to condemn Israel.
The parliamentary speaker, Ali Larijani, said Israel's actions were worse than the Nazis during World War II.
The United States and Britain receive daily tirades, as do Arab countries, accused of not going to the aid of the Palestinians.
The Iranian foreign ministry spokesman has said Iran's hospitals are ready to care for Palestinian wounded.
It all fits in with the pattern of vehement anti-Zionism that has been one of the defining features of the Islamic Republic for 30 years.
Pressure on Israel
But even as Hamas comes under intense pressure from Israeli forces, the Iranian government's response so far has been carefully calibrated.
Iran is one of the strongest supporters of Hamas.
It is regularly accused by Israel of providing the group with arms, training, and money, something Tehran never admits to, but makes little effort to deny.
But until now there has been little evidence of pressure from Tehran on its Lebanese allies, Hezbollah, to break the ceasefire on Israel's northern border.
So there is intense interest in whether the rockets fired from southern Lebanon early on Thursday came from Hezbollah.
If Hezbollah was responsible, the finger will quickly be pointed back to Tehran.
There is certainly a logic to Iran stepping up the pressure on Israel now.
The Iranian government does not want to see any deal in Gaza that restricts Iran's ability to send weapons and money to Hamas.
That would undermine a key plank of its regional strategy. There are already plenty of signs that Iran is working with its allies to prevent a ceasefire on such terms.
The influential Mr Larijani was in the Syrian capital Damascus on Wednesday, for talks with Iran's allies in Hamas, Hezbollah and the Syrian government.
On the same day, the Syrian foreign minister gave a tough interview to the Hezbollah TV station, al Manar, where he urged Hamas to stand firm.
The Hezbollah leader, Hassan Nasrallah, also hardened his position in a speech on Wednesday.
The meaning of this will only become clear once it is found out who fired the rockets from southern Lebanon into Israel.
Already, for President Ahmadinejad of Iran, the crisis has been a godsend.
At home he can mobilise hardliners in favour of his campaign to be re-elected in June, and distract attention from Iran's ever-increasing economic problems.
At the same time he can further his aim of promoting Iran as a leader of popular Arab, Muslim, and anti-American feeling, just as he did during the Lebanon war in 2006.
There have been frequent protests denouncing Israel's Gaza attacks
Just for good measure, the Iranian authorities have taken the opportunity for a crackdown on government opponents.
The Nobel Peace Prize-winning human rights lawyer, Shirin Ebadi, has had to flee her home in Tehran, after a mob gathered outside accusing her of supporting the Israeli military action.
She has made it clear she opposes the Israeli attack. The protest could not have happened without Iranian government support and probably encouragement.
Hardliners have also ransacked a Tehran branch of Benetton, an Italian-based clothing chain, that rather bizarrely has been accused of supporting Zionism.
So once again, Iran's government is taking advantage of another regional crisis, just as it did in 2006.
Israel already sees its battle with Hamas as a proxy battle against Iran.
The question now is whether the confrontation between Israel and Iran moves centre stage, to become an all-out battle for supremacy in the Middle East.