ABC News’ Olivia Katrandjian reports:

Protesters set fire to an American flag outside the U.S. Embassy in London today during a minute of silence to commemorate the moment the first hijacked plane crashed into the World Trade Center on Sept. 11, 2001.

Among the protesters in Grosvenor Square were members of the group Muslims Against Crusades (MAC). They shouted “USA terrorists” and held signs that read “Islam Will Dominate the World.”

(Carl Court/AFP/Getty Images)

“You will always face suffering, you will always face humiliation, unless you withdraw your troops from Muslim lands,” said one protester in a speech, according to multiple reports.

A smaller counter-demonstration was held nearby, with protesters holding signs reading “Muslims Against Extremism” and “If You Want Sharia, Move To Saudi.”

“I’m a Muslim. What they’re doing is bringing shame on all Muslims. This is not part of the teachings of Islam,” said Abdul Sallam, 41, who was waving a sign that read “Keep The Silence,” according to multiple reports. “Islam is all about peace, but what they want to do is hate other people. Islam teaches you that when you see anything bad or evil, you should speak out against it. If the moderate Muslims all came out and spoke out, that would defeat them.”

Earlier, a group of 60 protesters from the English Defense League (EDL), a far-right movement against Islamic extremism in England, were asked by police to move to make room for the anti-American protestors in Grosvenor Square. But the protesters did not go quietly.

EDL supporters threw glass bottles at the MAC protesters as police tried to disperse the group to prevent a confrontation, according to ITN. Twenty people were arrested for breaching the peace.

Later, as police struggled to move the MAC protesters towards the Central London Mosque in Regents Park, they arrested another four people.

One man spit at a photographer who was snapping a picture of him in the arms of policemen.