( CNN ) -- The death toll from clashes between Yemeni security forces and protesters rose to 13 , an activist said . The clashes occurred in the cities of Sanaa and Taiz on Wednesday , said Ibrahim Mothana , an activist who said he spoke to doctors . The death toll could rise as he was trying to get reports on victims in at least three other hospitals , Mothana said . CNN could not independently verify his report . Witnesses said Yemeni security forces used live ammunition fired on protesters in Sanaa and Taiz on Wednesday . Doctors and witnesses in the cities told CNN that 169 more people had been injured , some critically . `` Security forces are aiming for a massacre in Sanaa , '' said Abdul Wahab Anesi , a medical staff spokesman at a field hospital set up in Change Square . Before Republican Guards began firing at protesters in the square , they reportedly clashed with military personnel who had been protecting demonstrators gathered there . Journalists , medical sources and other witnesses told CNN that these soldiers defected two months ago along with Maj. Gen. Ali Mohsen Al-Ahmar , who withdrew his support from President Ali Abdullah Saleh in late March . At the time , he promised to protect civilians demonstrating against the president . In addition to the casualties in the capital , three people were killed and four were reported critically injured in Taiz . `` The attack took place while we were chanting , 'One more week left for you , Saleh , ' '' said Sabir Ali , a protester in Taiz . The protesters were giving Saleh a week to step down , saying if he does not , they will make good on a vow to march to the presidential palace . Earlier , a senior security official denied that forces fired on protesters in Taiz .
Death toll could be even higher , an activist says . Live ammunition is used against protesters in Sanaa and Aden , they say . At least 169 people are injured by bullets , grenades or batons in both cities , they say . The Republican Guard fought military personnel who were protecting demonstrators .