UPDATE 1-Some abducted schoolgirls returned to Nigeria's Dapchi - witnesses

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ABUJA, March 21 (Reuters) - Some of the 110 schoolgirls abducted from the northeast Nigerian town of Dapchi last month were brought back on Wednesday, two witnesses said.

People from the town said the girls were returned by men they thought were fighters from the Islamist militant Boko Haram group. They did not say how many girls had come back.

A military officer at a checkpoint near Dapchi told Reuters: "Boko Haram have brought the girls."

The kidnapping on Feb. 19 of the girls aged 11-19, was the biggest mass abduction since Boko Haram took more than 270 schoolgirls from the town of Chibok in 2014 - a case that triggered international outrage.

The Dapchi abduction has piled pressure on President Muhammadu Buhari, who came to power in 2015 promising to crack down on Boko Haram's nine-year-old insurgency and could face the voters again next year. (Reporting by Afolabi Sotunde in Abuja and Ola Lanre in Damaturu Writing by Paul Carsten Editing by Andrew Heavens)