The intervention comes as Spanish police confirmed on Monday the identity of the driver suspected of killing 14 people in last week's attack in Barcelona.
Officials say he is 22-year-old Younes Abouyaaqoub and the manhunt has been extended across Europe.
Also on Monday, a youth was due to appear in court in Finland in connection with the attack in Turku in which two women were murdered in the town's marketplace.
Speaking of the Barcelona attack, European Parliament President Antonio Tajani said, "I want to condemn, in the most resounding terms, the terrorist attack and my thoughts are with the victims of this terrible atrocity and their families, as well as the citizens of Barcelona. Barcelona is close to the heart of all Europeans."
The Italian MEP added, "I would also like to express my solidarity with the whole country, the Spanish King and the Prime Minister. My full support goes to the work being carried out by the Spanish authorities with the hope that they will stop the barbarity perpetrated by the terrorists in the shortest time possible.
"The determination of the European Union in the fight against terrorism will not diminish. We will not be intimidated by those who peddle violence and death and we will face them down strengthened by our freedom, our unity and rule of law."
On the Finnish attack last Friday, European Commission President Jean-Claude Juncker said, "We strongly condemn this unprovoked attack which happened only hours after the horror that unfolded in Spain."
He went on, "My thoughts are with the victims and their loved ones. I express my full solidarity with the security forces working to keep people safe on the ground, as well as with all the people of Finland and Prime Minister Juha Sipilä. The European Commission is at their full disposal for any support they may need."