Russian forces attacked an evacuation route for civilians trapped in the besieged port city of Mariupol Tuesday — violating a ceasefire agreement, Ukraine’s foreign ministry said.

The convoys were set to travel between Zaporizhzhia and Mariupol, in southeastern Ukraine, along a route pre-approved with Russia. Civilians and foreign students were told they would be free from fire.

The humanitarian corridor was meant to be open until 9 p.m.

“Russian forces are now shelling the humanitarian corridor from Zaporizhzhia to Mariupol,” the ministry tweeted.

“8 trucks + 30 buses ready to deliver humanitarian aid to Mariupol and to evac civilians to Zaporizhzhia. Pressure on Russia MUST step up to make it uphold its commitments.”

The corridor was suspected to be a trap Monday, with a senior Red Cross official telling the BBC that agency workers trying to use a passageway out of Mariupol said the route had been booby-trapped with landmines.