Saudi-led coalition forces reportedly carried out an air strike against a detention center in Yemen Friday, killing at least 70 people injuring over 100, and drawing condemnations from the United Nations, BBC reported.

Amjad Yamin, who handles communications for Save the Children in Yemen, said “[t]o wake up to this level of civilian death toll is honestly horrifying,” while U.N. Secretary General Antonio Guterres said the “escalation needs to stop.”

At least three children were also reportedly killed in the strike.

In a statement released Saturday, the coalition denied intentionally targeting the detention center, according to The Washington Post. “The target in question” lacked the “distinctive symbols and preventative measures” necessary to mark it as non-military and had “not been placed on the No Strike List (NSL) in accordance with the agreed upon mechanism,” the statement read.

Saudi Arabia and its allies intervened in Yemen’s civil war in 2015 after Iranian-backed Houthi rebels seized the nation’s capital. Watchdog groups have reported widespread human rights violations, and some U.S. lawmakers have called for a moratorium on arms sales to Saudi Arabia.

The Saudi-led coalition stepped up its air campaign this week after Houthis claimed responsibility for an attack on Abu Dhabi, the capital of coalition partner the United Arab Emirates.