Shocked by the Orlando massacre, gays around the world on Monday flocked to vigils for the victims of one of the deadliest attacks in the history of the gay rights movement. From Berlin to Bangkok, gay and lesbian groups organised gatherings in solidarity with Americans after Sunday's massacre at a gay nightclub that left 49 people dead in the worst mass shooting in modern US history. The Sydney Harbour Bridge was lit with the rainbow colours of the gay community flag as hundreds gathered to condemn terror and homophobia. "This could have happened anywhere," Australian Paul Savage told AFP at a candlelit vigil for the victims on the busy strip that hosts Sydney's annual Mardi Gras pride march. "He could easily have walked into a bar in Sydney," he said, pointing out that Australia's tighter gun laws were "much more helpful" in preventing the mass shootings that claim hundreds of lives each year in the United States. - 'Could have been us' - In Berlin, more than 100 people gathered outside the US embassy to lay flowers, light candles and wave rainbow flags. Helmut Metzner, a leading member of the Lesbian and Gay Federation in Germany, condemned what he called an attack on the global gay "family". "It could have hit any single one of us," he told AFP, adding: "We must stand united and defend our lifestyle and not back down. That is what the terrorists want, and that's a favour we won't do them." US President Barack Obama denounced the attack at the Pulse nightclub by slain shooter Omar Mateen, which also wounded 53, as "an act of terror and an act of hate". In an outpouring of solidarity similar to that seen after the Paris and Brussels attacks, social media were awash with messages of support for the families of the victims. Using hashtags such as #loveislove or #lovewins, many shared images of ribbons -- some black, others carrying the Stars and the Stripes of the US flag on one side and rainbow colours on the other. Global landmarks were swathed in the colours of the rainbow, with Paris' Eiffel Tower set to follow suit Monday night after similar displays lit up New York's One World Trade Center and Sydney's iconic bridge. "Paris is with Orlando," tweeted Anne Hidalgo, mayor of Paris, which is still recovering from the November jihadist attacks in which 130 people were killed. The Islamic State group, which was behind the Paris and Brussels attacks, also claimed responsibility for the Florida bloodshed. - 'Stop hate' - Whether Mateen, a US national of Afghan origin who had homophobic tendencies, was part of a wider jihadist conspiracy, as claimed by IS, remains unclear. German lawmaker Cem Ozdemir, co-chair of the left-leaning Greens Party, told AFP that whatever the outcome of the investigation, "Islamism and homophobia are two sides of the same coin." In one of several vigils across the United States, hundreds gathered in New York's Greenwich Village on Sunday to leave flowers beside a sign reading "Stop Hate". Despite the defiant tone struck at many of the gatherings, some people expressed fear. "It does scare me a bit, being gay and working in a gay bar," admitted Saleem Khan, a 30-year-old barman in London's Soho district, the heart of the city's gay scene. Obama said the FBI was investigating the latest in a string of mass gun killings in the United States "as an act of terrorism". French President Francois Hollande reacted "with horror" to the attack, which threatens to increase anti-migrant hostility in Europe where populist xenophobic parties are on the rise as the continent struggles with its worst migration crisis since World War II. The prime minister of Belgium, where 32 people were killed in jihadist attacks on Brussels' airport and metro in March, also sent his condolences. And German Chancellor Angela Merkel appealed for tolerance. "Although such deadly attacks cause profound sadness in us, we are resolved to continue with our open and tolerant lifestyle," she said on the sidelines of a visit to China. Pope Francis expressed shock at Mateen's "homicidal folly and senseless hatred". The condemnation was echoed by Russian President Vladimir Putin, who has cracked down on gay pride events. "Nothing can justify killing of civilians," President Ashraf Ghani of Afghanistan tweeted.