By Estelle Shirbon ABUJA, Jan 29 (Reuters) - Nigerians lined up for hours at outdoor voter registration posts on Monday in a last-minute rush to participate in landmark elections, but many complained about poor organisation. The April elections should mark the first democratic handover from one civilian government to another in Africa's most populous nation and top oil producer, which was ruled by the army for most of its post-independence history. The deadline for registering to vote was extended by two months to Jan. 30 after the process got off to a slow start in October because of a dearth of registration machines. The Independent National Electoral Commission (INEC) has said it aimed to register about 70 million voters and had brought in 34,000 machines to do so. The government gave the day off to all civil servants on Monday so that they could register. "I've been here for more than five hours trying to get registered. I want to vote because it's my right. That's why I'm suffering in this queue," said Celestin Onah, a 28-year-old salesman, as he waited at an INEC post in the centre of Abuja. "There are not enough machines. They are making it too hard for people to register. I am doubting if the government is really ready for this election," he said, sweating in the equatorial heat. INEC opted to use machines that store voters' thumbprints and headshots in an effort to reduce fraud on polling day. But the choice has been controversial because the machines are powered by batteries that require electricity to recharge every few hours. Power cuts that last for hours are a daily problem in Nigeria, while many areas have no electricity at all. INEC has used portable generators to recharge the batteries but they have not always been available or refuelled on time. TEMPERS FRAY In addition, INEC has had to rotate machines around several posts because it does not have enough to man each spot every day. Voters say they have struggled to find places to register. "I had to leave my area and trek to this place because I could never find the INEC people at their post near my house," said Joe Igba, a 41-year-old civil servant who had waited for more than three hours on another street in Abuja. In another queue, tempers were fraying after the long wait and people were shouting at the INEC official in charge. "If we are waiting for five hours to register, how long will we have to wait to vote? Or will the polling stations close before we can cast our ballots?" asked Rhoda Musa, a 36-year-old nurse, as she tried to elbow her way closer to the machine. Nigeria has a long history of vote rigging and political violence. These problems marred the last elections, in 2003, and INEC has said it was working hard to prevent any foul play. A spokesman said INEC was investigating why several machines were found in the houses of leaders of the ruling People's Democratic Party in southwestern Oyo state, where the party is divided over the disputed impeachment of the state governor. "INEC is likely to take legal action," he said. There were some in the long queues who put their faith in the electoral body to deliver a clean election. "It will be free and fair. This is the first time they are putting snapshots on the voters' registration cards. It will make it harder to cheat," said Bob Josiah, a 29-year-old construction worker. It was his third attempt to register. The machines' batteries went flat on the two previous attempts.