ANGELA UKOMADU and SEUN SANNI NIGERIAN police beat and arrested demonstrators yesterday as a small group protested over the reopening of the site where activists denouncing police brutality were shot last year in the commercial capital, Lagos, Reuters witnesses said. Rights group Amnesty International and witnesses have said soldiers opened fire on protesters on Oct. 20, killing at least 12 people at a toll gate in the city's affluent Lekki district and another area. The military has denied shooting live rounds and the police have denied involvement. There was a heavy presence of armed police officers on Saturday at the…