KYIV – Ukrainian police say a missing family of four has been killed in an antitank mine explosion near the front line in the eastern region of Luhansk, an area the United Nations has called one of the most mine-contaminated places on Earth.

Police officers discovered the bodies of a couple -- both man and woman were aged 57 -- their 38-year-old son, and his common-law wife, also aged 38, near the charred remains of a Chevrolet Niva.

The incident took place in a wooded area near the Siversky Donets River, which marks the front line between territory controlled by government forces and Russia-backed separatists.

The family members were residents of Pischane village in the Stanytsia Luhanska district of Luhansk region and were reported missing by a neighbor on April 7, according to police.

The International Committee of the Red Cross (ICRC) identified one of the women as Nina Vasylivna, a Pischane community leader who talked with the organization days earlier about raising chickens and growing vegetables in greenhouses to feed residents of the frontline village.

Police believe the family drove over an antitank mine with the car, resulting in a large blast that killed all four.

Photographs published to the website of Ukraine’s National Police show tire tracks beside a swathe of scorched earth several meters wide, the destroyed car, and what appears to be one of the bodies splayed out nearby.

Investigators first classified the incident as a homicide but have since changed it to a terrorist act.

Forensic experts, bomb disposal technicians, and members of an investigative team were still working at the scene on April 11, police said.

The United Nations Children’s Fund (UNICEF) has called the area of eastern Ukraine where fighting has entered its fifth year “one of the most mine-contaminated places on Earth.”

UNICEF and the ICRC have both repeatedly called on all warring parties to immediately end the use of mines, which they say have contaminated communities and put residents -- especially children -- in constant danger of injury and death.

More than 10,300 people have been killed since the conflict broke out in April 2014, according to the United Nations.