America on a knife-edge as racial tension boiling over
Police officers ordered to travel in pairs as hardline black activists promise a 'weekend of rage'
President Obama issued a call for unity yesterday, insisting that race relations in the US were not returning to the dark days of the 60s.
Mr Obama delivered his message as nationwide protests against police brutality towards black Americans led to further violence in the aftermath of the massacre in Dallas.
Demonstrations and vigils have taken place in more than 18 cities since Thursday night's march in Dallas, which resulted in a lone sniper murdering five police officers and wounding seven others in the worst attack on US law enforcement agencies since 9/11.
Mr Obama, who has announced he is abandoning a European visit and will arrive in Dallas in the coming days in a bid to calm race relations, called the killer "demented" and insisted he in no way represents America's black community.
Yesterday morning Rochester police chief Michael Ciminelli was forced to defend his officers after 72 protesters were arrested during a demonstration in New York State on Friday night. Among those detained were two black local news reporters from a local station, who were briefly handcuffed before police realised their mistake.
In Phoenix, Arizona, protesters in a several-hundred-strong rally hurled rocks at police lines. Officers - who later donned riot gear - responded with tear gas and pepper spray.
Tensions continued to run high in Baton Rouge, where Alton Sterling was shot dead by police on Tuesday. In the early hours of yesterday morning riot officers dispersed a rally of about 300 people.
In Philadelphia, protesters promised a "weekend of rage".
The protests, organised by the campaign group Black Lives Matter, which formed in 2013 to highlight police violence towards black people, have gained traction this week after videos emerged showing the 37-year-old Sterling and Philando Castile, 32, dying at the hands of police officers in Louisiana and Minnesota.
The group can mobilise thousands online. But its reach and power lies far beyond a disenchanted youth; instead tapping into America's increasingly entrenched racial and political divisions.
A study published by the respected Pew Research Centre last month found more than two-thirds of African Americans support the Black Lives Matter movement. Only a minority of white people - and just 20 per cent of Republicans - support it. According to the Washington Post, which has been mapping the killings, of 509 people shot or killed by the US police this year, 123 have been black, despite comprising only 12 per cent of the country's population.
The latest incident occurred yesterday, when officers shot Alva Braziel up to 10 times after he apparently pointed a revolver at them on a Houston street.
While violence flares elsewhere, in Dallas itself residents have come together in peaceful mourning. Among the mourners was Keaka Williams, the patrol partner of slain transit authority officer Brent Thompson.
The city's police, meanwhile, hope the outpouring of grief towards their fallen comrades may prove a much needed force for unity.
Detective Major Berry was on duty the night of the attack and knew all the officers killed. He was a close friend of 48-year-old Corporal Lorne Aherns, one of the last two victims to be named alongside 55-year-old Michael Smith.
Berry, a father-of-three who is black himself, admits "there is always going to be racial tensions between groups", but says police officers cannot be allowed to face "trial by social media".
Black extremist groups are nothing new in America. They rose to prominence in the mid-Sixties as an alternative to the non-violent stance of Martin Luther King, but in recent years they have found a new, more powerful tool than mass rallies: social media and the internet.
Micah Johnson, the gunman who killed five police officers in Dallas, was a follower of several of America's most violent black rights groups, but may never have attended any of their meetings or rallies.
A group calling itself the Black Power Political Organization claimed on its Facebook account that it was behind the attack, though there is no evidence Johnson had any connection to it.
Police are investigating whether he had become self-radicalised by reading material posted online by the likes of the New Black Panther Party (NBPP), the African American Defense League, the Nation of Islam and Black Riders Liberation Party.
He had either "liked" or followed them on his Facebook page, but told police before he was killed in a stand-off that he was not affiliated to any groups.
The term "self-radicalisation" has become familiar through the catalogue of Islamist terrorist attacks the world over, and the tactics used by Islamic State of Iraq and the Levant and others bear clear similarities to the worst extremes of black separatist groups. Johnson was, after all, doing exactly what these forums of boiling hatred have been telling their followers to do for years.
Dallas is the home of the New Black Panther Party (which has no link to the now-defunct 1960s Black Panthers) and its website has a document titled The Nationalist Manifesto which claims that white men have a secret plan to commit genocide against all non-white people.
It believes black Americans should have their own sovereign nation, and its 10-point platform calls for a country in which black people can make their own laws, with all black prisoners in US jails released to "the lawful authorities of the Black Nation".
King Samir Shabazz, head of its Philadelphia chapter, said in 2009: "I hate white people. All of them. Every last iota of a cracker [white person], I hate it … You want freedom? You going to have to kill some crackers! You going to have to kill some of their babies!"
The group reserves particular hatred for the police, who it calls "pigs".
The Southern Poverty Law Center, which monitors hate groups in the US, says there are 180 black separatist groups in the country, compared with 190 branches of the Ku Klux Klan (though neo-Nazi and other white power groups double that number).