Authorities reported Sunday that thousands of pieces of unexploded bombs from Cambodia's civil war had been discovered inside a school in the northeast.

A US bombing campaign and a bloody battle in the 1960s left the nation one of the world's most heavily bombed and mined. 

In three days, in Kratie province, deminers uncovered more than 2,000 bombs, including over 1,000 M79 grenades, inside a high school, according to Heng Ratana, director general of the Cambodian Mine Action Centre.

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Ratana told AFP that the bombs were discovered when the school plowed soil to create a garden and that the school has been temporarily locked down.

He called it a "stroke of luck" that the students had not triggered the explosives.

During the war, the location was a military installation, and it is likely that more explosives could be found. 

Cambodia's civil war continued until 1975, and nearly 20,000 Cambodians have died in the last 40 years from treading on landmines or explosives.

The government has promised to clear all mines and explosive ordnances by 2025.

Cambodia underwent a vigorous bombing campaign by the US between 1969 and 1973 and former US Secretary of State Henry Kissinger is considered by many to be responsible. 

According to Ben Kiernan, former head of Yale University's Genocide Studies Program, Kissinger is culpable for the death of as many as 150,000 civilians, up to 6 times the number of civilians killed in US airstrikes in Afghanistan, Iraq, Libya, Pakistan, Somalia, Syria, and Yemen.

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