Thousands of Egyptians have continued to occupy Cairo's Tahrir Square despite an offer from the military for a speedier handover to civilian rule. After four days of violent clashes, Field Marshal Mohamed Hussein Tantawi said presidential elections would be held by July 2012. But many protesters in the square said the concession was not enough and have demanded the field marshal step down. Clashes continued throughout the night between police and protesters in Cairo. Television pictures from Tahrir Square showed ambulances arriving to pick up injured people. According to Egypt's ministry of health, at least 30 people have been killed since Saturday and hundreds injured. Police have been using tear gas, rubber bullets and birdshot against protesters who have been throwing stones. Some protesters said live bullets had been fired. Clashes have also been reported in several other Egyptian cities including Alexandria, Suez, Port Said and Aswan. Frustration Egypt's ruling military council had previously said presidential elections might not happen until late 2012 or 2013. That move, coupled with a draft constitution produced earlier in the month that would exempt the military and its budget from civilian oversight, prompted a mass demonstration in Tahrir Square on Friday. Events turned violent when security forces attempted to remove the protesters from the square on Saturday. Many Egyptians have become frustrated with the slow pace of political reforms since Hosni Mubarak was overthrown as president in February after a wave of mass demonstrations. The Supreme Council of the Armed Forces (or Scaf) took charge after he was ousted and promised to implement the transition to civilian rule. Speaking on national TV on Tuesday, Field Marshal Tantawi, the head of Scaf, said parliamentary elections scheduled to begin on 28 November would take place as planned. Those polls, taking place over three months, are due to set in train the transition to democracy. The military's original timetable called for the new parliament to then choose a 100-member constituent assembly to draw up a new constitution within six months. A referendum would then approve the document before a presidential election was held. That would mean the military remaining in power until late 2012 or early 2013. Protesters, however, had demanded the presidential vote take place after the parliamentary elections. 'Not leaving' The BBC's Kevin Connolly in Cairo says the army's readiness to bring forward presidential elections appears to be a major concession. Field Marshal Tantawi said that the military was only there to protect the people and did not seek permanent power. "The armed forces, represented by their Supreme Council, do not aspire to govern, and put the supreme interest of the country above all considerations," he said. "They are fully prepared to immediately hand over power and to return to their original duty in protecting the homeland if that is what the people want, through a popular referendum if necessary." He also said he had accepted the resignation of Prime Minister Essam Sharif's cabinet - appointed by the military - and that a national salvation government would take its place. His announcement followed a day of crisis talks between the military and political leaders. After he spoke, protesters in Tahrir Square chanted: "We are not leaving, he (Tantawi) leaves." "We are not happy with this speech," a protester named Tamer Lokman told the BBC's Yolande Knell in Tahrir Square. "It reminded us of those made by the former president, Hosni Mubarak when he didn't answer our demands," he said.