Video message by Ayman al-Zawahiri seen as opportunistic by protesters calling for greater freedom and not Islamic rule

Syrian activists have rejected a message from the new al-Qaida leader, Ayman al-Zawahiri, praising their efforts to topple Bashar al-Assad as an Islamic battle against US and Israeli interests.

"I don't think a single Syrian would welcome this statement," said Razan Zeitouneh, a lawyer and rights activist in Damascus who has been monitoring the uprising. "Al-Qaida is trying to use our revolution to get back into the light after the peaceful Arab uprisings took attention away."

In a video message posted on extremist websites Zawahiri, who became al-Qaida leader in June following the death of Osama bin Laden, denounced Assad as "the leader of the criminal gang" and "biggest of those who spread corruption" – largely in tune with protesters' views.

But by calling the protesters "the front for jihad and martyrdom" he also sought to cast the uprising as sharing al-Qaida's aims – a far cry from protesters who have called for greater freedom, rather than the Islamist rule al-Qaida advocates.

Another activist who asked for anonymity dismissed the comments as irrelevant: "Al-Qaida has long been of no interest to Syrians and the statement comes too late in the day even if it had any weight," he said.

But activists said the regime, which made no comment, may try and use the statement to portray the protesters as armed Islamists and the uprising as a foreign conspiracy.

Mohammad Al-Abdallah, the spokesman of local co-ordination committees in Syria, said: "Zawahiri is trying to convince the world that he has supporters in Syria, which will provoke the international public opinion against us and give the regime the right to commit crimes against our people.

"We condemn such statements that are irrelevant to the revolution, Syrians chose the non-violent way for their revolution and they won't change it, they refuse any practices or speeches containing sectarian or violent properties."

Protests in Syria have come out of mosques because they are the only place where people are able to gather. There is a trend towards growing religiosity across the Arab world, but Syrians on the street appear to have little appetite for political Islam and have been calling for democratic reforms.

"Anyone observing the Syrian protesters for the last four and a half months can see they are peaceful, independent and keen for freedom," said Zeitouneh.

The activists' comments were echoed by the Foreign Office which accused Zawahri of "clutching at straws".

A spokesman for the Foreign Office told the Guardian: "We have seen al-Qaida struggle to show that its message of violent jihad is relevant to the Arab spring where people have found a different voice and a different way to bring about change they desire."

Zawahri claimed that Washington wanted to replace Assad with "a new ruler who follows America, protects Israel's interests and grants the [Muslim] nation a few freedoms".

The US administration has toughened its rhetoric toward Assad's regime, but no country has yet called on Assad to step down, causing frustration on the street.

"It's ironic that while the whole international community is silent about the regime's crimes against the Syrian people, a terrorist like Zawahiri says what he said," said Zeitouneh.

Nour Ali is a pseudonym for a journalist in Damascus