DHAKA (Reuters) - Police used water cannons and batons to disperse hundreds of supporters of Bangladeshs main opposition party who went on strike Monday to demand early parliamentary elections to force the ruling party from power. Scores of protesters were wounded in clashes with police, witnesses said, and media reported that at least 70 activists were detained. Analysts did not expect the general strike, the third by the opposition Bangladesh Nationalist Party (BNP) since Prime Minister Sheikh Hasina took office in early 2009, to bring forward the date of the 2013 general election. But it is a large-scale challenge by the BNP, emboldened by its success at municipal polls, and adds to the woes of Hasinas government, already struggling with discontent over high prices, lacking public services as well as the crash in the stock market, a main source of income for many in this impoverished country. At least five people were injured, two seriously, in clashes between protesters and police outside the BNPs central office in Dhaka, a Reuters reporter at the scene said. Police used batons and water cannons to drive the demonstrators back into the party office. Police also detained about 20 activists, the reporter said by telephone. Some 50 other protesters were injured and dozens detained in clashes with police outside Dhaka, media reports said. In December, food inflation hit 11 percent, its highest level in three years, and analysts warned rising global food prices may drive the index higher. Angry investors took to the streets of the capital on Sunday after the stock exchange suffered another dramatic fall, the latest of a series of collapses that forced halts in trading several times last month. Monday, the benchmark Dhaka Stock Exchange index shed 4 percent within two hours following its 5.7 percent slide on the previous day. Strikes have been often used by political parties in Bangladesh to force change, and senior BNP officials have vowed a fierce campaign to force early elections. But Shamsul Haque Tuku, state minister for home affairs, told the opposition to find other ways to protest. Strikes as a political weapon have become blunt and not enough to shake the government, he said. The strike was also intended to mobilise public opinion against a controversial new airport plan and force authorities to withdraw a case against BNP leader, Begum Khaleda Zia for allegedly provoking violence over the issue, BNP leaders said. The strike began at 6 a.m. and ends at 6 p.m. Prime minister Hasina defeated Khaleda in a vote held in December 2008 that restored democracy after two years of rule by a military-backed interim authority. Economists estimate that Bangladesh, home to more than 150 million people and a multi-billion dollar export-oriented garments industry, could lose some $250 million (154 million pounds) a day due to any strike-related stoppages. Analysts and diplomats say general strikes in the politically volatile country scare away investors and slow development. Any unrest could also cast a pall over Bangladeshs hosting of the Cricket World Cup on February 17.