Police in the Moroccan port city of Tangier have been searching the home of a prime suspect in the Madrid bombings.
Jamal Zougam is being held in custody by Spanish investigators of last Thursday's blasts which ripped through trains in the Spanish capital, killing 201 people.
The people of Tangier have shown solidarity with the Spanish victims
A neighbour of Zougam's Tangier home, in a middle class neighbourhood, said the suspect dressed in casual Western clothes and shaved off his beard when in Morocco, to avoid being stopped by the police.
The Spanish newspaper El Pais says police have identified Mr Zougam as one of six Moroccan nationals who they believe are responsible for the attacks.
Police say Mr Zougam and the five other Moroccans who are still at large were operating an Al-Qaeda cell within Spain.
On Tuesday, a crowd of 500 Moroccans gathered outside the Spanish consulate in Tangier, waving banners against terrorism and chanting for peace.
People in Tangier are especially angry that several of the prime suspects in the Madrid bombings come from the coastal town.
At the weekend, many joined the funeral procession through the streets of Tangier behind the weeping relatives of a 13-year-old girl and 24-year-old man.
They were two of three Moroccans killed in the Madrid attacks.
Some Moroccans showing their solidarity outside the Spanish consulate are hoping the Spanish police have made a mistake and the attacks will be traced back to the Basque separatist group Eta.
"Violence is against Islam," said one man at the demonstration, Abdelaziz. "I still believe Eta was responsible."
Other Moroccans are more resigned. "I'm not ashamed," said a woman called Khadija. "Terrorism has no nationality, but I am disappointed."
In the capital, Rabat, leaders of this Muslim country, including government ministers and members of the Moroccan royal family, attended a special Mass in the Catholic Church to commemorate the dead.
Outgoing Spanish Foreign Minister Ana Palacio spoke to the high-level congregation, thanking Moroccans for their support.
Minister of Communication Nabil Benabdallah was keen to show Morocco as a fellow victim at the hands of terrorism.
Mr Benabdallah said both countries had gone through difficult times
He told the BBC: "We wanted to express our solidarity with Spain and the Spanish people during these difficult times which we have also gone through with the 16 May attacks. That's why we say no to terrorism."
Moroccan police believe the prime suspect in the Madrid bombings, Jamal Zougam, may also be responsible for the Casablanca bombings.
Forty-five people were killed in the suicide bomb attack last May.
The fact that he and others wanted in connection with the attacks were still at liberty almost a year later raises questions about the Moroccan authorities' response to the bombings.
There have been thousands of arrests and almost weekly trials in Morocco since May, as the authorities crack down on Islamic extremism.
But privately, foreign security officials and civil society groups say the Moroccan security services are using too fine a net and failing to reel in the big fish.
The majority of convictions are for "belonging to a group with criminal intent", commonly taken to mean Salafiya Jihadia, a shadowy Moroccan movement the authorities say has links to Al-Qaeda.
Abdelatif Merroun is serving five years for being a member of criminal group. However, his wife Fatima says no evidence was produced at her husband's trial, and he was not permitted to call witnesses.
Human rights groups in Morocco have also expressed concern at the way in which trials of suspected Islamic radicals are carried out, with defendants often tried in batches with only 15 minutes each to testify.
Perry Jensen, a British man acquitted on these charges in August, said: "The Moroccan police are simply arresting anyone with a beard."