Nigeria’s main opposition lashed out at the government on Wednesday in a series of New Year’s messages as political rhetoric rises six weeks before much anticipated general elections.

Ex-military ruler Muhammadu Buhari, who is challenging President Goodluck Jonathan in February 14 polls, told “disappointed and angry” voters that in 2015 he would restore Nigeria as “a country that you can be proud of”.

Separately, his All Progressives Congress Party (APC), accused Jonathan’s government of using the security services as part of a campaign aimed at “decapitating” the opposition.

The APC statement alleged that the intelligence agencies and the police had been ordered by Jonathan’s government to crackdown on key opposition leaders in the run up to the polls.

While no senior APC leaders have been arrested to date in the campaign, one of the party’s most prominent members, House of Representatives Speaker Aminu Tambuwal, was teargassed by police as he tried to enter parliament last month.

In his own holiday season message, Jonathan pledged that the vote would be “free, fair, credible and acceptable,” but analysts have voiced concern about rising tension ahead of the vote.

The International Crisis Group said in a report last month that political rhetoric on both sides needed to be significantly lowered to reduce the prospect of unrest.

Buhari voiced “unshakeable faith that 2015 will be a year of change,” but experts still see Jonathan as the favourite, with the ruling Peoples Democratic Party having controlled the presidency since the end of military rule in 1999.

While Buhari’s policy credentials have been questioned, some see the former army general as better placed to contain the Boko Haram uprising in the mainly Muslim north, where more than 13,000 people have been killed since 2009.