Versailles - French President Francois Hollande vowed on Friday to improve the protection of a police force reeling from a terror attack and under pressure from violent protesters and football hooligans."Police officers risk their lives. We owe them respect and gratitude," Hollande said at an emotional memorial service in Versailles near Paris for a policeman and his partner who were killed by a jihadist.Hollande said the couple were "everyday heroes who fell victim to a hate-filled terrorist".Police commander Jean-Baptiste Salvaing and his partner Jessica Schneider were knifed to death on Monday by a convicted extremist who had pledged allegiance to the Islamic State group.Larossi Abballa, 25, was shot dead by police after he killed the pair at their home in the Paris suburb of Magnanville, in the presence of their 3-year-old son Mathieu who was traumatised but unhurt.Investigators are looking into whether Abballa knew his victims.Hundreds of uniformed police officers and firefighters, many fighting back tears, took part in the ceremony, where the pair were decorated post-posthumously with the Legion of Honour - France's highest award. The attack was the first of its kind in France since November 2015, when 130 people were killed by ISIS gunmen and suicide bombers in Paris.WeaponsFrance has since remained under a state of emergency, allowing officers to wear their weapons at all times - not only when they are on duty.Hollande vowed that measures would be taken to guarantee the anonymity of police officers, and said the gun-carrying measure should be permanent."Police and gendarmes must be given the means to defend themselves when they are not on duty. We must also avoid police and gendarmes being identified and targeted by criminals they have jailed, or their accomplices."Measures will be taken to guarantee their anonymity and thus, their protection," Hollande said.France's police force has been sorely tested by the high state of security, which has coincided with months of violent anti-government protests in which they have been a particular target of hatred and suffered dozens of injuries.Paris police chief Michel Cadot recently wrote a letter to the interior minister complaining that officers were overstretched and "exhausted" even before the start of the Euro football tournament on June 10.The European championship has seen running battles between police and football hooligans in several cities around the country."Violence against representatives of public order will never go unpunished," Hollande said.