(ANSA) - ATHENS, 12 MAR - Thousands of demonstrators staged fresh protests in Greece on Sunday as anger grows over the country's deadliest rail crash, ratcheting up pressure on the government over the tragedy. Protesters flooded Athens' Syntagma Square in front of parliament, waving banners that read "We won't forget, we won't forgive" and "We will become the voice of all the dead". Fifty-seven people, many of them students, were killed when a passenger train and freight train collided head-on in central Greece on February 28. Four railway officials have been charged but public anger has focused on long-running mismanagement of the network, and the country has been rocked by a series of sometimes violent mass protests. On Sunday about 12,000 demonstrators gathered outside parliament while 5,000 took to the streets of the second city Thessaloniki, police said. (ANSA).