By Matthew Tostevin and Camillus Eboh
ABUJA (Reuters) - Nigeria's ruling party looked set to see its strong grip on parliament weakened as votes emerged on Sunday from an election that observers said was the fairest for decades in Africa's most populous nation.
Election officials and party agents tallied results from 120,000 polling units stretching from the oil-producing mangrove swamps and teeming cities near the southern coast to the dustblown fringes of the Sahara desert in the north.
There were isolated reports of ballot box snatching, clashes between rival supporters in parts of the Niger Delta and two bombs in the remote northeast during the vote but observers said it appeared to have been a vast improvement on previous polls.
"I think it is fair to say this was a real election. It was a real vote," said Kenneth Wollack, president of the National Democratic Institute (NDI), who had also monitored other polls since military rule ended 12 years ago.
There were nonetheless challenges to results in some areas, including in the Niger Delta oil region -- where protesters forced their way into the electoral commission offices -- and in the capital Abuja, both ruling party strongholds.
The vote was seen as a test of whether electoral officials could organize smooth polls and make a break with a long history of elections discredited by ballot stuffing and thuggery.
President Goodluck Jonathan's ruling People's Democratic Party (PDP) was losing out to the opposition Action Congress of Nigeria (ACN) in the southwest and the Congress for Progressive Change (CPC) in parts of the north.
The ruling party nevertheless made gains in some areas.
Of those seats declared for the House of Representatives by 1900 GMT, the ruling party had just over half compared to 77 percent in the outgoing parliament. Less than a third of the seats had been declared, however.
The speaker of the House of Representatives, Dimeji Bankole of the PDP, lost his seat, while the daughter of former president and PDP stalwart Olusegun Obasanjo lost her bid to remain in the Senate.
"Nigerians have freely spoken for once," said Emma Muogbo, a lecturer in the southeastern city of Onitsha. "Now committed people could come up to serve knowing that if they fail to do well, people could vote them out."
The PDP was declared the winner of the two House of Representatives seats and one Senatorial seat in the capital Abuja although it was a close race in many wards and the opposition CPC questioned the outcome.
Opposition parties in Bayelsa, Jonathan's home state in the Niger Delta, also refused to accept losses there.
"I demand that the elections be canceled with immediate effect and a new date be set," said Imoro Kubor, governorship candidate for the ACN in the state, alleging that voting materials and results sheets had been given to PDP supporters.
Saturday's election, delayed by a week because of widespread logistical glitches, was the first in a cycle which includes presidential elections on April 16 and governorship polls in the country's 36 states on April 26.
"The fact we've done this despite all the hitches has set the mood for the biggest election in black Africa," said Dafe Akpedeye, head of the Swift Count local monitors group.
The African giant has failed to hold a single vote deemed credible by observers since the end of military rule in 1999.
Most Nigerians say the closest the country came to a free election was in 1993, polls which were annulled by former military ruler Ibrahim Babangida, helping pave the way for another six years of military rule.
(Additional reporting by Nick Tattersall in Lagos, Ibrahim Mshelizza in Hawul, Austin Ekeinde in Port Harcourt, Anamesere Igboeroteonwu in Onitsha; Writing by Nick Tattersall; editing by Joe Brock)