SPANISH police intensified a manhunt Friday for suspects behind two deadly vehicle attacks on civilians, shooting and killing five people wearing fake bomb belts who attacked a seaside resort and arresting four others believed linked to the carnage wrought on a Barcelona promenade.

Spanish authorities said the back-to-back vehicle attacks Thursday afternoon and early Friday morning — as well as a deadly explosion earlier this week in a house elsewhere in Catalonia — were related and the work of a large terrorist group.

The Daesh (so-called IS) group quickly claimed responsibility for Europe’s latest bout of extremist violence, which left 13 dead and 100 wounded after a van roared down Barcelona’s historic Las Ramblas promenade on Thursday. Hours later, a blue Audi plowed into people in the popular seaside town of Cambrils, killing one person and injuring five others.

Spanish Prime Minister Mariano Rajoy declared Friday that the fight against terrorism was a global battle and Europe’s main problem.

Police said they arrested two more people Friday, after an initial two were arrested Thursday — three Moroccans and one Spaniard, none with terror records. At least three of them were nabbed in the northern town of Ripoll. Another arrest was made in Alcanar, south of Barcelona, where a gas explosion in a house Wednesday that killed one person was also being investigated as a focus of the probe.

Amid heavy security, Barcelona tried to move forward Friday, with its iconic Las Ramblas promenade quietly reopening to the public and King Felipe VI and Rajoy joining thousands of residents and visitors in observing a minute of silence in the city’s main square.

“I am not afraid! I am not afraid!” the crowd chanted in Catalan.

But the dual attacks unnerved a country that hasn’t seen an extremist attack since 2004, when Al-Qaeda-inspired bombers killed 192 people in coordinated assaults on Madrid’s commuter trains. Unlike France, Britain, Sweden and Germany, Spain has largely been spared, thanks in part to a crackdown that has netted some 200 suspected militants in recent years.

World leaders have condemned the attack, expressing outrage and solidarity with the victims.

The Spanish royal family issued an unusually strongly-worded statement: “They are assassins, criminals who won’t terrorize us. All of Spain is Barcelona.”

FC Barcelona said it was “deeply saddened” by the tragedy and the team’s talismanic striker Lionel Messi said separately that people must reject “any act of violence”.

“There are many more of us who want to live in a world in peace, without hate and where respect and tolerance are the basis of coexistence,” he added.

President Donald Trump tweeted: “The United States condemns the terror attack in Barcelona, Spain, and will do whatever is necessary to help. Be tough & strong, we love you!”

Secretary of State Rex Tillerson added: “Terrorists around the world should know -- the United States and our allies are resolved to find you and bring you to justice.”

In a statement, the office of German Chancellor Angela Merkel said they were thinking of the victims of the “revolting attack” with “profound sadness”.

President Vladimir Putin called for the world to unite in an “uncompromising battle against the forces of terror”.

“We decisively condemn this cruel and cynical crime against civilians,” Putin wrote in a telegram of condolences to Spanish King Felipe VI.

A spokesman said UN Secretary General Antonio Guterres “condemns today’s terrorist attack on Barcelona” and “hopes that those responsible for this heinous violence will be swiftly brought to justice.”

British Prime Minister Theresa May tweeted: “My thoughts are with the victims of today’s terrible attack in Barcelona ... and the emergency services responding to this ongoing incident. The UK stands with Spain against terror.”

London Mayor Sadiq Khan called the attack “barbaric”, adding: “London stands with Barcelona against the evil of terrorism.” — Agencies