Lagos, Nigeria (CNN)Violent protests following Nigeria's presidential elections Saturday have sparked calls for calm from the two main candidates and a warning by the U.S. and Britain against political interference.
Protesters fired gunshots and torched a local electoral office in Nigeria's oil-rich Rivers state on Sunday as they marched to protest the elections, amid claims of vote-rigging and voter intimidation.
Heavy rain eventually forced the protesters to leave, but there are fears that it will take more than rain to stop further protests and violence. More than 800 people were killed in post-election violence across Nigeria's north in 2011 after charges that those elections were illegitimate.
Now Nigeria has just held what are thought to be the closest elections since a return to democracy in 1999 after decades of military rule. The two main candidates are incumbent President Goodluck Jonathan of the Peoples Democratic Party and retired Gen. Muhammadu Buhari of All Progressives Congress.
Jonathan and Buhari last week issued a pledge reaffirming their commitment to "free, fair and credible elections" following their signing of the Abuja Accord in January.
After the protests in Rivers, Buhari's All Progressives Congress demanded the elections there be canceled. "There's been so much violence in Rivers state that it's just not tenable," party spokesman Lai Mohammed said.
But the Peoples Democratic Party disputed the accusation, saying the election was "credible and the result reflects the overwhelming wish of the people of Rivers state to support President Goodluck Jonathan."
Concerns over count
"We are concerned by what seems to be happening," said Attahiru Jega, Nigeria's election chairman, about events in Rivers. Voting has now ended after problems with ballot papers and digital voting cards saw it extended to Sunday in some areas, and results are starting to come in.
Britain and the United States entered the fray Monday with their top diplomats issuing a statement welcoming a "largely peaceful vote" but warning any political interference would contravene Jonathan and Buhari's peace pact.
"So far, we have seen no evidence of systemic manipulation of the process. But there are disturbing indications that the collation process — where the votes are finally counted — may be subject to deliberate political interference. This would contravene the letter and spirit of the Abuja Accord, to which both major parties committed themselves," U.S. Secretary of State John Kerry and UK Foreign Secretary Philip Hammond said.
The fear is that the results may not be accepted by the loser. If the opposition believes it has been rigged out of victory by the ruling party, then the protests in Rivers could spread to northern Nigeria.
Both candidates have taken to social media to call for calm.
"I want to urge all Nigerians to also wait patiently for the Independent National Electoral Commission, INEC, to collate and announce results," stated Jonathan on his Facebook account.
"Fellow Nigerians, I urge you to exercise patience and vigilance as we wait for all results to be announced," said Buhari on Twitter.
In a broadcast to the nation Friday, Jonathan said security agencies were fully prepared to deal decisively with "any group or persons who attempt to disrupt the peaceful conduct of the elections."
"Those who may harbor any intentions of testing our will by unleashing violence during the elections in order to advance their political ambitions should think again as all necessary measures have been put in place to ensure that any persons who breach the peace or cause public disorder during or after the elections are speedily apprehended and summarily dealt with according to our laws," the President said.
The International Criminal Court also issued a warning that anyone inciting or engaging in electoral violence "at a time when abhorrent levels of violence already plague parts of the country" is subject to prosecution, "either by Nigerian Courts or by the ICC."
"No one should doubt my Office's resolve to prosecute individuals responsible for the commission of ICC crimes, whenever necessary," ICC Chief Prosecutor Fatou Bensouda said in the statement.
Nigeria's polls had been scheduled for February 14, but on February 7, Nigeria's election commission announced they would be postponed for six weeks due to security concerns, with the military needing more time to secure areas controlled by extremist group Boko Haram. The controversial decision was unpopular among many Nigerians and led to widespread protests.
Jonathan has been criticized for not doing enough to combat Boko Haram, which is waging a campaign of terror aimed at instituting a stricter version of Sharia law in Nigeria.
On Saturday, residents in the northeastern state of Gombe said at least 11 people were killed and two more injured in attacks at polling stations, apparently by Boko Haram extremists.
In other attacks not believed to be related to voting, suspected Boko Haram militants decapitated 23 people in a raid Saturday night on Buratai village in northeast Nigeria's Borno state, according to residents and Ibrahim Adamu, a local politician in the village.
Meanwhile on Monday, Nigeria's police force issued a statement saying police and a "local vigilante group" had foiled an attack by unknown gunmen on the town of Tafawa Balewa in northeastern Bauchi state.
The assailants had "stormed Tafawa Balewa town in a convoy of 18 Hilux vehicles and started firing sporadically," the statement said. After being forced to retreat and abandon four vehicles equipped with anti-aircraft machine guns, the attackers went to Jitar village, where they killed three "male vigilante members," police said. Security forces had cordoned off the surrounding area, they said.