NEW : Protesters launch fireworks into government building in Kiev early Sunday morning . NEW : Opposition says police were using the building to launch attacks on them . The president also said he would agree to a working group to look at changes to the constitution , according to the president 's website . On Saturday the opposition leaders rejected Ukrainian president 's peace offer . Comment:
NEW : Protesters launch fireworks into government building in Kiev early Sunday morning . NEW : Opposition says police were using the building to launch attacks on them . On Saturday the opposition leaders rejected Ukrainian president 's peace offer . Comment: