Supporters rides in a campaign bus of Nigeria's leading opposition All Progressive Congress (APC) presidential candidate Mohammadu Buhari and his unning mate Yemi Osinbajo in Lagos on January 24, 2015. Unknown gunmen stormed and bombed the site of a ~ PIUS UTOMI EKPEI
Port Harcourt - One police officer has been killed, four others have been injured and a reporter covering the event was stabbed at the APC election rally.
The violence erupted at the opposition All Progressives Congress (APC) meeting of governorship candidate Dakuku Peterside in Okrika, the hometown of President Goodluck Jonathan's wife Patience.
"Five police officers were shot. One of them is dead and four are lying in critical condition at this hospital," Peterside said.
Peterside and a source at the private Channels television network said its reporter at the scene, Charles Erukaa, had been stabbed and was being taken to a hospital.
Political tensions have raged in Rivers state since outgoing governor Rotimi Amaechi defected to the APC from the ruling Peoples Democratic Party (PDP) in 2013.
The war of words has been particularly fierce between Amaechi's camp and supporters of the first lady.
Critics have alleged that she sees Rivers as her personal political domain and was committed to removing the governor at any cost.
Peterside, who is Amaechi's hand-picked successor, had tried twice previously to hold a rally in Okrika but was forced to cancel on security grounds.
Also read: Bomb goes off at APC rally
As supporters were gathering for Tuesday's rally at the National Secondary School, several explosions went off, Peterside told journalists.
Organisers then decided to press on with the event but gunshots from unknown assailants caused a second wave of chaos, live pictures on Channels showed.
Erukaa was forced to take cover, lying with his stomach on the ground as armed security personnel moved in the background. He was later stabbed in the leg by unidentified attackers.
Police were not immediately available to comment on the identities of the gunmen. Peterside claimed the gunmen were PDP loyalists but that claim could not be independently confirmed. - Swing state -
The National Human Rights Commission last week said 58 people had been killed in political violence in the run up to Nigeria's polls, which were initially scheduled for February 14 but have been moved to March 28 over security fears.
The commission pointed to oil-producing Rivers in the Niger Delta as a flashpoint area for potential unrest, in part because of the bitter rivalry between the APC and the first family in the state.
In the national campaign, Jonathan is facing a tough test against the APC's Muhammadu Buhari, a former military ruler, and Rivers has been identified as a key swing state.
Jonathan comes from neighbouring Bayelsa and had previously banked on massive support across the Niger Delta but Amaechi's defection to the APC has changed the political dynamics.
Losing Rivers could ruin Jonathan's re-election hopes and would likely be seen as a personal embarrassment to the first lady, who is an often criticised figure in Nigeria.
Patience Jonathan had initially suggested that the kidnapping of more than 200 schoolgirls in Chibok by Boko Haram in April last year was staged to embarrass her husband.
Later, while meeting with relatives of the hostages, she appeared to fall into a religiously inspired trance, repeatedly shouting "there is God-o!", a video of which went viral in Nigeria.