WASHINGTON - US Secretary of State Hillary Clinton, in a telephonic call to spokesman of Egypts new Vice President, Omar Suleiman, urged him to conduct an investigation into violence that rocked Cairos Tahrir Square. She emphasised our condemnation of the violence that occurred today and the responsibility of the government to hold fully accountable those who did it, said Philip Crowley, the State Department spokesman. Crowley said the US doesnt know who is behind attacks on protesters, which left more than 1,000 injured, according to the Al Jazeera television network. Whoever they are, there needs to be accountability here, Crowley said. This was clearly an attempt at intimidating the demonstrators. Supporters of Egypts President Hosni Mubarak clashed in central Cairo with demonstrators who were demanding an immediate end to the 30-year tenure of the leader. Mubarak said Tuesday he planned to stay in office until elections, scheduled for September. The US has called on Mubarak to begin the transition of power immediately. Tomorrow is not good enough, Crowley said. The US wants to see elections in Egypt as soon as possible, Crowley said. What we want to see is a credible process that leads to free, fair, legitimate elections. Crowley said the US has no plans to reduce the $1.5 billion in military and economic aid it provides to Egypt. He said, however, This is something we will continually review based on ongoing events. Crowley praised the Egyptian army for its professionalism and said it was in the difficult position of trying to be a stabilising force without being forced to choose sides. The army will obviously play a role in this transition, Crowley said. President Barack Obama dispatched former Ambassador Frank Wisner to Egypt, where the diplomat told Mubarak on Jan 31 that his time in office was coming to an end. Wisner, who is still in Egypt, also met with Suleiman, Crowley said. The US has had no official contact with the Muslim Brotherhood, Egypts largest opposition group, Crowley said. The State spokesman said the US wouldnt object if the Brotherhood took part in future elections. The group is legally banned from politics, so its members campaign as independents. They are a fact of life in Egypt; they are highly organised, Crowley said of the group. If they choose to participate and respect the democratic process, those are decisions to be made inside Egypt. Crowley said the US wouldnt try to anoint a particular candidate in any future election. This is not our process, he said. Our point is this transition, this process to fundamental change, needs to begin now. Clintons remarks come as Egypts main opposition group, Muslim Brotherhood, urged the United States and its Western allies to stop supporting President Mubarak. Muslim Brotherhood said the US should instead back the Egyptian people, adding that the US approach towards the Egyptian uprising would be decisive for the future of Cairo-Washington relations. Crowley, in a nod to the ripple effects of Egypts upheaval, said the US would hope the next government of Egypt would play a constructive role in the peace process between Israelis and Palestinians. He dismissed calls by Suleiman for the demonstrators to go home before dialogue begins. I dont think its credible to say no dialogue can begin until the protesters leave the streets, Crowley said. Reuters adds: White House spokesman Robert Gibbs said on Thursday the Egyptian government must not target journalists covering anti-government protests, and reiterated that the time for political transition was now. Any journalist that has been detained should be released immediately, Gibbs told reporters travelling with the president, adding that acts to intimidate the media were completely and totally unacceptable. At least six people were killed during overnight fighting in Cairo between anti-government protesters and those loyal to President Hosni Mubarak, whose offer to quit power in September has been rejected by an opposition that wants him out now.