A week of largely peaceful anti-government protests intended to "shut down" Bangkok took a dangerous turn on Friday when a lunchtime bomb blast killed one man and injured 35 others, stoking fears of further violence in a nation prone to bloody street wars.  Bangkok's emergency services centre said 36 people were injured in the blast, most not seriously. One of the wounded, who had been hit in the chest by shrapnel and suffered massive blood loss, died early on Saturday, the centre said.  The explosion took place when a grenade landed on a lorry driven by protesters during a march. It is unclear if protest leader Suthep Thaugsuban – a former opposition politician who has vowed to rid Thailand of corruption and nepotism – was the intended target, or if the attack was meant to "scare" protesters from continuing their movement, which aims to oust prime minister Yingluck Shinawatra from power.  Police investigating the explosion allegedly found a cache of weapons in an abandoned building near the blast, along with a "red cap" – a clue, or perhaps a red herring, said analysts, related to the colour-coded politics that pit pro-government "red shirts" against anti-government "yellow shirts".  In an interview with the Guardian, "red shirts" leader Tida Tawornseth denied her group's involvement in the violence and said she and other leaders had specifically told members to stay at home during the demonstrations to avoid any conflict.  "We want to save lives, we don't want a civil war. We will not come out because if we come out it will be very dangerous – we want to avoid violence."  Tens of thousands of protesters have taken to the streets over the last two months calling for Yingluck to quit, alleging she is a proxy of her brother Thaksin – a billionaire tycoon ousted as PM in a military coup in 2006.  Armed with whistles, clappers and placards, these opponents of the "Thaksin regime"– which they say is rooted in money politics – want to see government reform take place before any election, and have called for Yingluck to step down and an unelected "people's council" installed in her place.  Although Yingluck has called for a snap election on February 2 in an attempt to appease protesters, the opposition Democrat party has decided to boycott it, leading to a political stalemate that analysts say could become increasingly violent if left unchecked.  "The window is narrowing," political scientist Panitan Wattanayagorn of Chulalongkorn University said. "Yingluck has two problems: she has the political crisis to handle, but now with this attack she has the looming larger security crisis at hand too. She needs to pressure the police chief to send able units to control whatever is going to happen … because if Suthep is injured or killed then you have a big, big problem at hand.  "You need to control Suthep at all costs – it's like protecting Yasser Arafat."  The protests to date have killed eight and injured hundreds more, with Friday's explosion following small bouts of violence this week that have been waged largely at night, including grenade attacks on PDRC supporters such as Bangkok's governor, Sukhumbhand Paribatra, and former Democrat premier Abhisit Vejjajiva, who lost the 2011 election to Yingluck.  The political instability, which has seen protesters camp out on Bangkok's busiest intersections and forced Yingluck's government to relocate to offices north of the city, is costing the "land of smiles" an alleged £20m a day in lost revenue and has sparked concerns over a possible military or judicial intervention.  Suthep, who was uninjured in Friday's attack, has called for protesters to lay siege to government ministries, cut water and power to ministers' private homes, and even abduct Yingluck if she refuses to resign. On Friday evening he once again took to a rally stage in yet another call to arms, asking protesters to march on Saturday morning across the country.  A few miles away from Suthep's stage a candlelight vigil was taking place, where hundreds of Thais in white shirts were calling for peace and calm amid the growing chaos.  "Even though democracy here in Thailand is not complete, elections are the only starting point to create change for the better," said "Bird", a 47-year-old musician. "A coup d'état won't help anything but create more violence."  • Additional reporting by Praves Hongjanya
More than 30 people are hurt after explosive device is thrown into lorry driven by demonstrators during march in Thai capital