Gunmen in Nigeria have kidnapped the elder brother of Nigerian and Everton football star Joseph Yobo, police say.Norum Yobo was seized at a hotel in Port Harcourt, a spokeswoman said. No group has yet claimed responsibility and no ransom has been demanded.Everton football club said it would do all it could to help Joseph Yobo, who is on holiday in Lagos.Kidnappings, frequent in the oil-rich Niger Delta region of the country, have mostly ended with a ransom payment.Rivers State police spokeswoman Rita Inoma-Abbey told BBC Sport that an investigation had been carried out at the hotel where Norum Yobo was seized."We have not heard anything yet from Mr Norum or the kidnappers but we will make a statement available as soon as we can establish contact with them," she said.The family has confirmed the incident, which occurred in the early hours of Saturday morning, but otherwise declined to comment.BBC Sport reporter Oluwashina Okeleji in Nigeria says kidnappings - more often of oil workers - have become a common occurrence in the south of Nigeria.Although Nigeria is Africa's top oil producer and the bulk of that oil comes from the Niger Delta area, the region remains deeply impoverished, he says.Source: Joseph Yobo