"We are thinking with profound sadness of the victims of the revolting attack in Barcelona -- with solidarity and frienship alongside the Spanish people," tweeted spokesman Steffen Seibert.
Thirteen people were killed and more than 100 remain in hospital after a suspected Islamist terrorist drove a van into pedestrian on the bustling Las Ramblas street in Barcelona.
Citizens from 24 countries were killed or injured in the attack.
The German foreign office has said it is working to confirm reports that German citizens are among the dead.
Catalan authorities have confirmed that Germans were also among the injured without revealing numbers.
Three people have been arrested in connection with the attack, the deadliest in Spain since 192 people were killed by Al Qaeda-inspired terrorists in the 2004 train bombings in Madrid.