Lagos - The main opposition party on Wednesday accused the country's security services of being politically partisan and of conducting a "witch-hunt" against it before next year's elections.
"We are worried about the way institutions of democracy are being deployed to rubbish or witch-hunt the opposition," All Progressives Congress (APC) spokesman Joe Igbokwe told AFP.
"The security agencies are clearly taking sides."
Igbokwe was speaking after officials from Nigeria's secret police, the Department of State Services (DSS), allegedly raided the party's data centre in Lagos and seized documents.
It was the second such raid in 10 days.
Also read: PDP says APC data centre an affront to democracy
After the first, on November 22, the DSS said it acted on information about the alleged cloning of voters' cards "with the intention of hacking" into the electoral agency's database.
The APC, which has strongly denied the allegation, accused the DSS of becoming "one of the enforcement arms" of President Goodluck Jonathan's ruling Peoples Democratic Party (PDP).
Igbokwe said that neither the APC officials arrested during the first raid nor the documents seized have been released.
DSS officials did not respond to calls when contacted on Wednesday.
Presidential, parliamentary, gubernatorial and state assembly elections are slated for February next year, with Jonathan seeking a second, four-year term.
But tensions have increased between the PDP and the APC, which have led to fears of widespread election-related violence.
Last month, police and the security services teargassed the speaker of the lower House of Representatives after he and fellow opposition members were locked out of parliament before a key vote.
Igbokwe said the security agency's actions were "not good for democracy" and claimed that PDP politicians who had defected to the APC recently had been harassed.