KINSHASA (Reuters) - Police fired tear gas to disperse supporters of Democratic Republic of Congo s opposition chief on Sunday as they gathered in the capital amid high tensions over election delays keeping President Joseph Kabila in power, a Reuters witness said. Felix Tshisekedi, head of an opposition coalition, is due to fly back to the capital Kinshasa on Sunday after a prolonged absence abroad. Around a dozen supporters had gathered at his family residences in the morning, although there was no sign of violence.  Tshisekedi intends to call for a civil disobedience campaign in order to pressure Kabila, whose mandate expired last year, to step aside. Congolese authorities banned the coalition s planned meeting on Sunday, citing a risk of violence in the Central African country of more than 70 million people.  