After chanting "Allahu akbar", those gathered for Friday prayers at Brussels' Grand Mosque streamed outside to chant "Long Live Belgium," feeling the pressure to tackle radicalisation after the attacks on the city.
"The time has come to act," Imam Ndiaye Mouhameth Galaye told AFP ahead of his sermon. "Today we're launching a programme against radicalisation."
As the faithful arrived, the Belgian and European Union flags fluttered at the entrance to the city's main mosque, close by EU headquarters and several embassies.
"These criminals committed barbaric crimes," the imam said. "We are going to tell them that what they did has nothing to do with Islam."
"Friday's sermon," he told hundreds gathered in the prayer room, "will focus on current events."
Condemning the attacks in which 31 people died and 300 were injured, the Senegalese-born imam said Muslims were "sad and sorrowful" and urged the crowd "to give their blood" to those wounded.
Once the prayer session was over, the faithful gathered outside the building in one of the city's parks, the Cinquantenaire gardens that surround the mosque, chanting "Long Live Belgium."
Followed by a few dozen men and women bearing bouquets, Galaye headed to the Maalbeek metro station about a kilometre (900 yards) away to pay tribute to the dead at the site where one of three bombers blew himself up on a train.
A Muslim man reads from the Koran at the Grand Mosque in Brussels on March 25, 2016.
The mosque, which also hosts the Belgian Islamic and Cultural Centre (CICB), opened in 1978 thanks to Saudi Arabia, which has faced criticism for its hardline interpretation of Islam and its global funding of religious centres often seen as breeding grounds for jihadists.
"We're not financed by Saudi Arabia, we're financed by the World Islamic League," the imam said.
"Of the 400 or 500 youngsters who've left for Syria (from Belgium), not a single one studied with us.
"It all happens on social media, on Internet and most of them are former delinquents, criminals."
'Dealers and gunmen'
The shock of the attacks has prompted the mosque to work with young people to fight radicalisation.
"We've repeatedly condemned what happened in Paris and elsewhere. The time has come for action. Belgium's been hit," the imam said.
The CICB aims to launch a programme targeting youth that would involve theologians practising a moderate Islam, he added.
A picture taken on March 25, 2016 shows a banner reading "not on behalf of Islam" as people gather to pay tribute to the victims of the Brussels terror attacks, on Place de la Bourse.
Though the details have yet to be finalised, Galaye said the project is almost up and running. He said he had often provided counselling for families worried about their children becoming radicalised.
"We try to contact them and have already stopped several young people from leaving for Syria. Some are currently studying here now," he said.
Outside the mosque, one young man said, "Muslims aren't terrorists", while another added, "We're very sad about all this, it has to stop."
"(The terrorists) are all drug dealers and gunmen," said 25-year-old Sohaib Ben Ayad. "We don't have to justify ourselves as Muslims, we too know people who were hurt at the airport or on the metro."
Loubna Lafquiri, a young Belgian-Moroccan mother of three, was killed in the blast on a metro train at Maalbeek station.