ISTANBUL (AFP) - Police firing pepper gas and water cannons clashed with union activists in Istanbul on Thursday, as workers around the world made soaring food prices their May Day battle cry. In Cuba meanwhile, President Raul Castro also led hundreds of thousands of Cubans summoned to Havana's Revolution Square, although the focus of that rally was the future of the country after a change of leadership there for the first time in over half a century. Clashes erupted as hundreds of police surrounded the main square in Turkey's biggest city to stop a planned rally. Police detained 505 people in the Istanbul clashes. The police assault forced demonstrators into a building where they crowded windows, chanting "We are the people, we are right, we will win." Six police and two demonstrators were injured, according to officials quoted by Anatolia news agency. Volatile crowds also staged rallies in the Philippines' capital of Manila and Indonesia's Jakarta, carrying signs demanding "Jobs, Justice, Food" and "Lower Food Prices Now." Sharply rising prices for staples such as rice were the focus of many demonstrations in Asia, where rallies were patrolled by huge numbers of police. Jakarta police chief Adang Firman told reporters after monitoring the capital from a helicopter that 10,000 security personnel had been deployed and another 50,000 were on standby. Elite police commandos armed with assault rifles were positioned on highways leading to Manila. In Singapore and Bangkok, protesters waved signs reading "Expensive rice prices, cheap labour wages. How can labourers live?" The benchmark Thai rice variety now fetches some 1,000 dollars a tonne, three times more than a year ago. Fears over fuel prices were also on people's minds, with about 44,000 people attending a rally in Tokyo where Japanese Communist Party leader Kazuo Shii railed against the government for reinstating a controversial petrol tax. In Havana, meanwhile, Raul Castro sat listening in his four-star general's military uniform as Salvador Valdes, leader of the lone Workers' Union, called on some 11 million compatriots to "ratify our decision to continue on the path set out by the founder of the Cuban Revolution, Comrade Fidel (Castro)." Castro, 76, replaced his ailing brother Fidel, 81, as president in February. Many analysts say Raul Castro is under intense pressure to deliver improvements in Cubans' standard of living. In communist China, business came to a standstill as China celebrated the national holiday. Huge traffic jams blocked some roads out of Beijing and the expressway to the Great Wall had tailbacks at least 20 kilometres (12 miles) long. More than two million people joined Mayday demonstrations in 1,000 towns across Russia, Ria Novosti news agency said, with worries about soaring prices overshadowing official calls for unity a week ahead of Vladimir Putin's departure from the Kremlin. In Germany, tensions over a neo-Nazi party forced a major security operation to separate rival rallies in Nuremberg and Hamburg. In Greece, transport and public services ground to a halt as unions called a 24-hour May Day strike against a privatization drive and pensions reform. Ferry boats and intercity trains were reduced to a minimum, all train connections to foreign destinations were cancelled and state carrier Olympic Airlines carried out only one flight per destination. No newspapers were published while radio and television stations operated on reduced staff, the main journalists' union ESIEA said. France's interior ministry told AFP almost 120,000 people came out across the country as calls were made for higher wages and pensions, upping the pressure on President Nicolas Sarkozy to tackle rising living costs. In South Africa, ANC leader Jacob Zuma told a rally that state social security aid for 12 million citizens is now "under strain due to the rising cost of living." African trade unions meanwhile called for a cancellation of interim trade accords with the EU that replaced preferential tariff agreements early this year. The International Trade Union Confederation-Africa's secretary general Kwasi Adu-Amankwah said the richer European Union arm-twisted Africa into the deals. Burundi bucked the international trends, deciding to delay labour day celebrations to allow the overwhelmingly Christian population to mark Ascension Day on Thursday.