Parts of the Bronx burned Monday night as looters had free rein to ransack scores of small businesses — chaos that finally prompted Mayor Bill de Blasio to order extra cops to swarm the areas.

“Fordham is on fire,” the blog Uptown Collective said, calling it an “ominous sign” alongside video of at least half a dozen fires burning in trash-strewn streets.

Other video showed dozens of looters racing from a jewelry store as cops pulled up close to the fires.

“How are we destroying our own communities and are ok with it?” Jose Daniel Rojas asked alongside his video. “There are serious problems we need to address.”

The mayor tweeted early Tuesday that he had “just left the Bronx.”

“Real problems on Fordham Road, also Burnside Avenue. Spoke with Councilman Fernando Cabrera about immediate steps to address the situation,” he said.

“Also spoke to Commissioner Shea + Chief Pichardo, who are sending additional help.”

Uptown Collective said the looting “is not good for communities of color.”

“Protest is called for but destroying our own community is not,” it stressed.