A deadline is approaching for striking workers at the South African mine where police shot dead 34 miners on Thursday to go back to work or face dismissal. A statement from mine owner Lonmin said 3,000 workers were striking illegally and must report to work on Monday. The company delayed the deadline from Friday in light of the killings at the Marikana platinum mine, north-west of Johannesburg. Some miners said the new ultimatum was an insult to their dead colleagues. President Jacob Zuma on Sunday declared a week of national mourning. About 3,000 rock-drill operators (RDOs) at the mine walked out more than a week ago in support of demands for higher pay The strike was declared illegal by owner Lonmin, the world's third largest platinum producer. 'Final ultimatum' The miners, who are currently earning between 4,000 and 5,000 rand ($484-$605), say they want their salary increased to 12,500 rand ($1,512). "The final ultimatum provides RDOs with a last opportunity to return to work or face possible dismissal," Lonmin said in a statement on Sunday. "Employees could therefore be dismissed if they fail to heed the final ultimatum." It also told 25,000 non-striking workers and 10,000 contractors, all of whom have been unable to work as a result of the violence, that the police consider it safe to return to duty. Initially, employees were asked to report only for their morning shift. Staff have also been issued with contact numbers to report cases of intimidation. "The safety and security of our employees is paramount and nobody will be asked to report for duty if the police consider them in danger of reprisals," chief financial officer Simon Scott said. "The vast majority of our workforce, and their families, who rely on our mine for their livelihood, have now been unable to work for more than a week." 'Insult' Some miners dismissed the call as disrespectful to their colleagues who died. "Expecting us to go back is like an insult. Many of our friends and colleagues are dead, then they expect us to resume work. Never," worker Zachariah Mbewu told AFP news agency. He said no-one would return to work as long as they were still in mourning and that workers would only go back when management gave them what they sought. The circumstances that led police to open fire on Thursday remain unclear, but reports from eyewitnesses suggest the shooting took place after a group of demonstrators, some holding clubs and machetes, rushed at a line of police officers. Police, armed with automatic rifles and pistols, fired dozens of shots. At least 78 people were injured in the violence and some 250 people were arrested. Announcing the week of mourning on Sunday, Mr Zuma said the nation was in "shock and pain". "We must this week reflect on the sanctity of human life and the right to life," he said. Flags will fly at half mast at all flag stations in South African and missions outside the country during the mourning period, which will last from Monday until next Sunday.