Activists are accusing Nigeria's government of intimidating and harassing the judiciary after several senior judges were detained in weekend sting operations.

Nigeria's intelligence services announced more than $800,000 had been seized in raids targeting judges from the country's high courts. The Department of State Services said it had been monitoring the judges' "expensive and luxurious lifestyle" amid complaints they had accepted bribes.

It did not specify how many judges were in custody.

Civil society groups quickly cried foul. The Socio-Economic Rights and Accountability Project said it was "seriously concerned" about the arrests and called on all judges to be released immediately.

In a statement Sunday, the office of President Muhammadu Buhari said all arrests and searches were carried out according to the law in a bid to root out corruption.