Syria’s government said it has agreed to a conditional cease-fire starting late Thursday in northwestern Syria, according to state media. Government troops and allied Russia warplanes have been carrying out a three-month offensive against the rebel’s last stronghold, which has displaced hundreds of thousands and has targeted health facilities and other infrastructure.

The decision came hours after U.N. Secretary-General Antonio Guterres authorized an investigation into attacks on health facilities and schools in the rebel-held enclave, following a petition from 10 members of the U.N. Security Council.

The offensive in Idlib and surrounding areas has unfolded since April 30, displacing more than 400,000 people and killing hundreds. Images of attacks on health facilities and residential homes were reminiscent of the peak of the violence in the eight-year conflict. International rights groups, western countries and the U.N. had appealed for a cease-fire. Around 3 million people are living inside the rebel-held area.

A war monitoring group, the Syrian Observatory for Human Rights, said there was no sign of a cease-fire. It said intense clashes continued on the southern edge of the rebel stronghold.