NEW : Police pen hold demonstrators in for hours , a protester says . Students are angry about government plans to cut tuition increases . A large crowd filled the streets near Parliament in London . Other protests are reported in Leeds , Cambridge and Oxford .
NEW : Police pen student demonstrators in for hours , a protester says . Students are angry about government plans to allow tuition increases . A large crowd filled the street near Parliament in London . Other protests are reported in Leeds , Cambridge and Birmingham .