Yenagoa, Nigeria – Nigeria's ruling party on Monday won the key oil-rich state of Bayelsa, the electoral body said, a sign of President Muhammadu Buhari's growing influence in opposition strongholds.Forty-five candidates had taken part in the gubernatorial election on Saturday, which was marred by sporadic violence, including killings, abduction, vote-buying, snatching of voting materials and voter intimidation.Bayelsa has been ruled by the opposition Peoples Democratic Party (PDP) since Nigeria returned to civilian rule in 1999.It is a key political battleground because of the lucrative oil and gas sector that is largely based in the southern delta region.David Lyon of Buhari's All Progressive Congress (APC) won more than twice the number of votes as his closest rival Douye Diri of the PDP, said the Independent National Electoral Commission.In a statement on Monday, the president congratulated the new governor, but deplored the violence that characterised the vote."Violence during elections vitiates our commitment to demonstrate to the world and upcoming generation that we are a people capable of electing leaders in a peaceful and orderly manner," he said, urging those unhappy with the results to seek legal redress, rather than resort to violence.'Big boost for APC, Buhari'Political analysts see the APC's victory in an opposition stronghold as a sign of Buhari's growing influence."The victory is a big boost for APC and Buhari. It's a measure of acceptance and popularity of the president and his party in the core oil-rich region of which Bayelsa is a part," said Dapo Thomas, a politics and history lecturer at Lagos university."I think it is also a reflection of the changing voting pattern of the people in the region who want to be part of the central government headed by Buhari."Bayelsa and central Kogi are among seven states where gubernatorial elections are being held at different times from the general election due to court rulings. The results of the Kogi election on Saturday were still awaited.Regional elections are fiercely contested in Nigeria, where governors are powerful figures, controlling state finances and responsible for key areas from education to health.Nigeria, Africa's most populous nation with 190 million people, has a long history of electoral violence.More than 50 people were killed during the February and March 2019 general election, which returned Buhari to power.In 2011, hundreds of people were killed in post-election violence, mostly in northern Nigeria.