WASHINGTON (AFP) - The United States expressed scepticism on Tuesday that more than 200 schoolgirls held by Boko Haram militants had been located by Nigeria, stating that it had no "independent information" on the matter.

The country's highest ranking military officer on Monday said that Nigeria had located the missing teenagers, kidnapped mid-April by the armed militant group.

But one day later, US State Department Spokesman Jen Psaki told journalists that the there was no "independent information from the United States to support these reports."

Asked whether she found it "smart" of Nigerian officials to announce they had found the girls - in the event that they had been located - Ms Psaki responded that "for the girls' safety and wellbeing, we certainly would not discuss publicly this sort of information."

With 80 US military personnel sent to neighbouring Chad for intelligence, surveillance and reconnaissance, the United States is the biggest foreign participant in the effort against Boko Haram.

Washington has also deployed surveillance drones, spy planes and about 30 civilian and military specialists to support Nigeria's security forces.

US authorities have previously expressed doubt that Abuja has the capacity to conduct the rescue mission.

State Department and Pentagon officials as well as members of Congress have chided Nigeria for what they called a slow response to the crisis and for human rights violations of which its army is accused.