London (CNN) -- The European Union is under cyber attack, a spokesman said Thursday, as a major international summit begins.
The attack is targeting the EU Commission -- its executive arm -- and the external action service, said Antony Gravali, a spokesman for the EU administration in Brussels, Belgium.
"I was alerted to this on Tuesday and we are taking urgent measures to protect the institutions," he said.
"All users have had to change their passwords, and we have suspended access to e-mail and the internal intranet from home as a precaution, but at the institutions our systems continue to work as normal," he said.
The attack was launched only days before the start of the EU summit, but Gravali said he had not seen any evidence that the attack was connected to the gathering.
"We frequently come under cyber attack, but it is not like we normally see a surge in attacks ahead of the EU summits," he told CNN.
An inquiry has been launched into the attack, but Gravali said it is "extraordinarily difficult" to find out the origins of cyber attacks.
Gravali would not specify what parts of the Information Technology infrastructure that had been attacked or who they suspected was behind it.
The attack was still going on Thursday morning, but employees at the institutions were still able to work "as normal" Gravali said.