Four Ukrainian civilians were killed when a minivan carrying them drove over a land mine as they waited to cross out of separatist-held territory in eastern Ukraine on 10 February, authorities said. Three passengers died instantly and another later from their injuries from the explosion around 12 miles south-west of the rebel-controlled city of Donetsk, with one passenger surviving the blast.

A fighter at a separatist checkpoint said: "It was an anti-tank mine. How did it happen? In the evening when they close down their checkpoint, they place mines on road. And as far as we understood, they simply forgot to take them away. Seems like they took them to the roadside and a car wanted to bypass the line and exploded at a check point."

Ukraine's military spokesman Andriy Lysenko confirmed that the incident happened on the separatist-controlled territory. "Today at 7.56am, a passenger minivan Volkswagen was blown up by an explosive device. The bus was travelling from the temporarily occupied territories. The accident happened 600m away from Mariinka checkpoint," Lysenko said.

"The vehicle was in a line of cars which moved from the territories under the control of the so-called DNR fighters. The vehicle driver moved to the roadside ignoring mines warning signs. There were five people in this vehicle. As a result of explosion three people died instantly, another passenger died on the way to hospital," he added.

There is still a substantial number of unexploded mines across the conflict zone, despite efforts to clear them. Fighting continues despite a year-old ceasefire agreement. Last week the head of the Organization for Security and Co-operation in Europe (OSCE), which monitors the implementation of the ceasefire deal, voiced deep concern over escalating violence in eastern territories. More than 9,000 soldiers and civilians have been killed since the conflict broke out in April 2014, when the pro-Russian separatists rose up following Russia's seizure of Ukraine's Crimea region.