January 15, 2015 11:16 AM EST

A new set of before and after satellite images released by Amnesty International shows two towns in Nigeria’s restive northeast were hit hard by the Islamist militant group Boko Haram in a days-long attack earlier this month.

Images provided by DigitalGlobe from Jan. 2 show Baga and Doron Baga before the assault. Ones from Jan. 7 then show, according to the international watchdog, that more than 3,700 buildings in both towns had been damaged or destroyed by fire since the pictures five days before. (Healthy vegetation is shown in red; and destroyed buildings are in yellow.)

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“These detailed images show devastation of catastrophic proportions in two towns, one of which was almost wiped off the map in the space of four days,” said Daniel Eyre, an Amnesty researcher on Nigeria. “Of all Boko Haram assaults analyzed by Amnesty International, this is the largest and most destructive yet.”

The death toll remains unclear, hovering between 150 and up to 2,000. An uptick in attacks by Boko Haram has cast a shadow over the country’s elections planned for next month.

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Write to Charlotte Alter at charlotte.alter@time.com.

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