Gambian president Adama Barrow paid tribute on Friday to three young protesters killed by police in an anti-pollution rally, urging witnesses to come forward to a commission of inquiry set up by his government."You are the people that witnessed what happened here that day," Barrow told his audience in the village of Faraba Banta, 50km from the capital, Banjul. "You are the most competent people to give evidence to the commission of inquiry."President Barrow - who last year succeeded the autocrat Yahya Jammeh - prayed at the local mosque before meeting the victims' families. "I have never been this sad since the day I became president of this country," he told residents.Locals have been protesting at Faraba Banta over the mining of sand which they say is badly polluting rice farms.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and FacebookTwo young men were killed on Monday and a 24-year-old student died in hospital on Wednesday. Five more civilians and 16 police officers were injured in the clashes, according to an official toll."God knows when I will be relieved of this pain," Ebrima Bah, whose brother Ismaila was killed in the clashes, told AFP. "I want the culprits that caused the death of my brother to be brought to justice."On Thursday, Barrow set up an inquiry into the incident and the inspector general of police, who said he had not authorised the use of guns on protesters, resigned.Human Rights Watch and Amnesty International cited witnesses as saying that demonstrators had been blocking mining-related road traffic when police reinforcements arrived and opened fire without warning. A protest at the end of May had seen police use rubber bullets and tear gas to disperse protestors.