United Nations chief Antonio Guterres says that attacks on civilian infrastructure are “unacceptable,” after Iran accused the United States of targeting bridges and transport hubs, AFP reports.

“The Secretary General remains deeply concerned by the continuing military escalation between Iran and the United States of America,” spokesman Farhan Haq tells reporters.

“He’s particularly concerned about attacks on civilian infrastructure in Iran and across the region. Such attacks are unacceptable,” he adds.

The United States has not confirmed Iran’s allegations that it targeted civilian sites.