The majority of those killed and injured were local Moroccans
Militant Islamists have been rounded up by police in the Moroccan city of Casablanca in connection with Friday night's series of bomb attacks.
At least 30 people were arrested in a major security operation across the city.
King Mohammed VI went to Casablanca on Sunday and began touring the sites targeted by the blasts, starting with the hotel Safir.
The King has called for a full and transparent investigation into the attacks -
a statement which seems designed to dispel suspicions that the authorities may carry out the investigation in secrecy and plant blame for the bombings without adequate evidence, the BBC's Sebastian Usher in Casablanca says.
A focus of the inquiries will be whether the attackers were connected to any local Islamic organisation, he says.
The Salafiyah Jihadiyah is suspected of having links to Osama Bin Laden's al-Qaeda network which is blamed for anti-Western terror attacks around the world, he adds.
At least 41 people were killed and about 100 injured in the five blasts that hit Casablanca within 30 minutes of each other.
The targets also included a Jewish community centre, a busy Spanish restaurant and social club, and the Belgian consulate.
King Mohammed has pledged to cover the medical costs of the wounded.
The explosions came amid worldwide terror alerts and just four days after a co-ordinated series of bombings in the Saudi Arabian capital, Riyadh, killed 34 people.
Morocco's Interior Minister Mustapha Sahel said there were similarities between the bombings in Casablanca and Riyadh.
The BBC's security correspondent Frank Gardner says there are indications that the Casablanca blasts were probably the work of a "North African cell linked to al-Qaeda".
In the past, Osama Bin Laden's terror network has carried out similar co-ordinated suicide bombings against Western or Jewish targets.
A team of French forensic experts are to join Moroccan investigators
But this was the first such devastating attack in Morocco - a staunch US ally which nevertheless opposed the war on Iraq.
A taped message attributed to Bin Laden and distributed to the media in February named Morocco on a list of "apostate" Arab nations.
In the same month, Morocco handed down 10-year jail terms to three Saudi men accused of forming an al-Qaeda cell and plotting to attack Nato ships in the Straits of Gibraltar.
Officials earlier said three suspects, all Moroccans, had been arrested soon after the co-ordinated attacks.
Two of them were reportedly based in the suburbs of the city, possibly operating close to the authorities.
Mr Sahel said a group of 14 people divided into five teams triggered the five blasts.
The bombings drew widespread international condemnation. France and the United States have offered to help find those responsible.
The authorities have already deployed extra police and soldiers across the city - especially outside hotels and restaurants - and set up checkpoints.
But correspondents say local people are angry that not enough was done to prevent the bombings in the first place, accusing the government of complacency.
Mr Sahel said the attacks bore "the hallmark of international terrorism", adding that 10 suicide bombers were among those killed.
King vows vengeance
A spokesman for King Mohammed, Hassan Aourid, said the attacks were "the work of blind international terrorism". He said the perpetrators would be punished "without mercy".
The king is expected to tour the scenes of devastation and meet victims on Sunday.
Officials said the dead were mainly Moroccans. Three French nationals, two Spaniards and an Italian were also killed, diplomats said.
Witnesses spoke of the attackers having grenades and other explosives tied to their belts.
The bombings came after a week of national festivities held to celebrate the birth of a new crown prince - the first child of King Mohammed.