"It is very true that for Nigeria you are facing a pretty severe slowdown because of what has happened with the oil shock," Oyin Anubi, sub-Saharan Africa economist at Bank of America Merrill Lynch, told CNBC on Monday.
"They are a very oil-dependent economy and consumption is very import-dependent."
The oil and gas sector accounts for about 35 percent of Nigeria's gross domestic product and petroleum exports represent over 90 percent of total exports revenue, according to the Organization of the Petroleum Exporting Countries (OPEC).
Since oil prices started their 50 percent slump last June, the Nigerian Naira has fallen by around 22 percent against the U.S. dollar.
The World Bank sees Nigeria's economic growth slowing to 5.5 percent in 2015 from 6.3 percent in 2014.
Doubts over the economic policies of current president, Goodluck Jonathan, mean his re-election is uncertain, despite the benefits of incumbency, said Alan Cameron, economist at Exotix Partners, a frontier market boutique investment bank.
"It is widely acknowledged that he hasn't run the economy very well. It has dented his popularity," Cameron told CNBC on Monday, adding that if oil prices was still around $110 per barrel he would probably get re-elected. Brent Crude is currently trading around $55 per barrel, however.
"I think there has been an acknowledgement that he hasn't performed very well and that has been highlighted by the fact that oil prices are down, the stock market's down, the currency's been devalued," he added.
"The country is clearly facing quite a difficult adjustment in the coming few months and it has made it very difficult for him to get re-elected, in what would otherwise have been almost a shoo in."
The decline in oil prices—as well as concerns about the security situation in the north-east of the country—has led some major corporate players to pull back from the country.
France's Total announced on Monday that it had completed the sale of its stake in an onshore Nigerian oilfield, taking its recent divestments in Nigeria to over $1 billion.
Outbreaks of violence during voting, as well as technical glitches which caused the election to be extended over two days, has further worried investors in the short-term.