Militants attacked and took control of the town, in Borno state, on Thursday evening, residents said.
The militants have repeatedly targeted villages around Chibok over recent months.
Boko Haram says it is fighting to create an Islamic state in Nigeria.
Residents told the Sahara Reporters news website that the militants headed to the centre of Chibok and declared that they were taking it over as part of their caliphate.
The schoolgirl kidnappings in Chibok caused worldwide outrage and sparked a social media campaign.
Since the kidnapping people have complained that the area was not well protected and many residents of Chibok had already moved to safer parts of the country, fearing another attack.
Boko Haram has changed tactics in recent months by holding on to territory rather than using hit-and-run attacks that have left thousands dead.
Last month, the group dismissed the government’s claims to have agreed a ceasefire. The government had said the ceasefire would set the stage for the release of the Chibok schoolgirls.
Chibok is a relatively small, mainly Christian town.
Its seizure comes a day after a government helicopter came down in Yola, in north-east Adamawa State – the second military helicopter to go down in the area in a week.
Officials and residents said the army had managed to recapture the town of Mubi, which was the biggest town under Boko Haram’s control.
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