* Police tear gas quells new disturbance in Port Sudan
* Violent unrest spreading over fuel subsidy cuts
* Economic crunch caused by oil-rich South Sudan's secession
By Khalid Abdelaziz and Ulf Laessing
KHARTOUM, Sept 26 (Reuters) - At least 29 people have been killed in protests in Khartoum over fuel subsidy cuts, police said on Thursday, and more clashes broke out in Khartoum in the ...