A Nigerian policeman has been sacked after being caught on film apparently trying to extort $150 (£100) from a motorist accused of a traffic offence.The footage - secretly filmed on a Lagos highway - received thousands of hits on YouTube and has been replayed on Nigerian television channels.In the film, Sgt Chris Omeleze suggests he is part of a wider corrupt network.But Nigeria's central police command insists otherwise. It sacked him less than a day after the video emerged.Correspondents say being asked for money by traffic police for real or imagined traffic offences is a common experience for many Nigerians.It is much rarer for perpetrators to be caught and penalised.'Reasonable' sumThe film - which has received more than 123,000 hits on YouTube - shows Sgt Omeleze inside the car trying to negotiate a bribe with the driver.He demands 25,000 naira ($150), but the driver - who was returning from Lagos airport - says he can only spare 2,000.In response, the police officer threatens to book the driver at the police station - unless he can come up with a "reasonable" sum.He says he would accept 1,000 naira, but he is "not working alone".Later, he sniffs that he has "related to you like my own brother and friend" but cannot accept such a low amount.He then appears to phone a colleague to explain that the driver is not co-operating and should be booked.The footage emerged on Tuesday and on Thursday. Police spokesman Frank Mba confirmed Sgt Omeleze had been fired the previous day."I want to gladly report that in less than 24 hours after we got wind of that story, the police officer was identified, arrested... [and] dismissed from the police force," Mr Mba was quoted as saying on Channels Television.But Mr Mba insisted Sgt Omeleze was working alone and had only pretended to call a colleague to try to "blackmail" the motorist.Sgt Omeleze was sacked after an "orderly room trial" - a term used in Nigeria for an internal police inquiry - in which the officer was "close to tears" and described his ordeal as the "handiwork of the devil", reported Sahara Reporters. He had a 21-year career in the police.Analysts say corruption is usually not the work of lone operators in Nigeria's police forces, but of officers working in corrupt networks extending far up the chain of command.