Prince William has said his thoughts are with those "confronting unimaginable grief" following the deaths of 22 people in the Manchester terror attack.
The Duke of Cambridge also said he was "shocked and saddened" to learn of the attack which left a further 59 people injured.
In a letter also written on behalf of his wife, the Duchess of Cambridge, and Prince Harry, the 34-year-old praised the people of Manchester "for their display of strength, decency, and community", calling it "an example to the world".
Flags outside the EU headquarters in Brussels are flying at half mast in the wake of the Manchester Arena attack.
All 27 EU flags - one for each country in the union - that line the approach to the building were lowered as a mark of respect for those killed and injured in the attack at an Ariana Grande concert in Manchester on Monday night.
Earlier in the day European Parliament President Antonio Tajani shared a message on behalf of parliament members saying "our thoughts and prayers are with the victims and families".