ABUJA (Reuters) - Nigeria's ruling party has lost control of at least two states in governorship elections, according to results emerging on Wednesday, although it performed strongly in some parts of the mostly-Muslim north. The state governorship races, which began on Tuesday, are the final stage in elections which have seen some of the worst political violence in years in Africa's most populous nation. Rioting left hundreds dead in the mostly Muslim north last week after President Goodluck Jonathan, a southern Christian, beat northern rival Muhammadu Buhari in the presidential vote. The state governors are among the most powerful politicians in Nigeria, wielding influence over national policy and in some cases controlling budgets larger than small African nations, and the ruling party is keen to maintain its strong regional grip. With results in from half of the 24 states in which governorship elections were held, the ruling People's Democratic Party (PDP) held on to seven but lost two - Ogun in the southwest and Nasarawa in the center. But it won Kano, the most populous state in the north, from the opposition and swept all assembly seats in the northern state of Sokoto. Lagos, the commercial capital, remained the southwestern stronghold of the opposition Action Congress of Nigeria (ACN) as expected while the northern state of Yobe remained in the hands of the All Nigeria Peoples Party (ANPP). Ballot box snatching and intimidation marred Tuesday's votes in some parts of Nigeria, but there was nothing on the scale of the violence last week which followed the presidential election. "Although in general there was low turnout, reports from observers indicate that the elections were well organised and largely peaceful in many states," said the Election Situation Room, a grouping of more than 20 civil society groups. "In other states, however, there were considerable reports of violence, ballot box snatching and other forms of electoral malpractice," it said in a statement. There were immediate cries of foul play. "We're going to contest the result in the court of law because this is not the true reflection of the votes by the people," said Musa Sule of the Congress for Progressive Change (CPC) in the northern state of Jigawa, won by the PDP. The ruling party said it would challenge the result in Lagos. Soldiers arrested people stealing ballot boxes in several states around the country on Tuesday, including parts of the oil-producing Niger Delta in the south and Kano in the north. Police on Wednesday confirmed the shooting of a member of a state assembly in the southern Delta state. The force said her driver was killed in the incident which it said was "ballot box snatching." The governorship vote is due to end on Thursday in the northern states of Kaduna and Bauchi, areas which saw some of the worst riots last week. This month's elections have been an emotional rollercoaster for the 73 million registered voters in Nigeria, which - until 11 days ago - had failed to hold a single credible election since the end of military rule in 1999. Euphoria over a presidential vote deemed free and fair by observers turned to despair last week as Buhari rejected the outcome and his supporters took to the streets, burning churches, mosques and homes. Tens of thousands of people are still sheltering in army barracks. Jonathan's PDP saw its parliamentary majority narrow in this month's polls and had also been expected to lose some states after Tuesday's vote. Buhari's Congress for Progressive Change, a new party, is expected to perform strongly in the north.