The self-proclaimed Islamic State of Iraq and Sham (ISIS) called on insurgents in Egypt's Sinai Peninsula on Monday to press ahead with attacks against Egyptian security forces and to continue beheadings, an appeal likely to deepen concerns over ties between the militant groups.Egyptian officials, including the foreign minister, have acknowledged coordination between the two groups but have said there are no ISIS fighters in the country. ISIS controls swathes of territory in Iraq and Syria where it has proclaimed a caliphate.Egypt has faced various insurgencies since the army ousted President Mohamed Mursi of the Muslim Brotherhood last year."Rig the roads with explosives for them. Attack their bases. Raid their homes. Cut off their heads. Do not let them feel secure," ISIS spokesman Abu Muhammad al-Adnani said in a statement released online.He praised Egyptian militants for carrying out "blessed operations against the guards of the Jews, the soldiers of Sisi, the new Pharaoh of Egypt".President Abdel Fattah al-Sisi, who as army chief last year led Mursi's ouster following mass protests, has expressed concerns about militants in Egypt and in other parts of the Middle East.A militant from the Sinai-based Ansar Bayt al-Maqdis, which has killed hundreds of Egyptian security forces over the last year, has told Reuters that ISIS has provided instructions on how to operate more effectively.On Sunday, a bomb attack beside the Egyptian foreign ministry in Cairo claimed by a militant group killed three policemen, including a key witness in a trial of Mursi.