WASHINGTON (Reuters) - Republicans on Monday continued their drive to loosen U.S. regulation, taking the first step to kill five Obama-era rules on corruption, the environment, labor and guns under the virtually untested Congressional Review Act.  The House Rules Committee sent to the full chamber three regulations enacted under former President Barack Obama, a Democrat, to ax. They were the Stream Protection Rule, the Securities and Exchange Commission’s “resource extraction rule,” and one on gun buying. Republicans put as much urgency on limiting what they consider over-regulation that stifles economic growth as they do on overhauling the tax code and dismantling the Affordable Care Act, according to House Majority Leader Kevin McCarthy.  This is the first time the Republican-led House of Representatives has targeted specific rules since convening on Jan. 3. Earlier this month it passed bills to limit regulatory agencies and Republican President Donald Trump is cutting regulation through executive orders. Under the law, Congress can use simple majority votes to stop recent regulations in their tracks. Agencies cannot create a new rule to replace any part of an overturned regulation. Timing in the law means any rules enacted in the final months of Obama’s administration are eligible for axing. The law has been used effectively only once, in 2001. Both sides consider this week a test of its powers.  On Tuesday the Rules Committee will send two more regulations to the full chamber, which is expected to vote to kill all five on Wednesday and then hand them off to the Senate. Senate Republicans on Monday prepared to act quickly after the House vote, with Majority Leader Mitch McConnell and Environment Committee Chairman James Inhofe introducing companion measures on the stream and extraction rules. The Interior Department took years to craft the stream rule, hoping to prevent coal-mining waste from contaminating water sources in areas near mountain-top removal mining sites. Critics say it is unnecessary and goes too far, wiping out jobs and usurping state rights. The extraction rule is required in the 2010 Dodd-Frank Wall Street reform law, but was only approved six years later this summer. It requires companies such as Exxon Mobil Corp (XOM.N) to state publicly how much they pay governments in taxes and other fees. Opponents say it hurts U.S. energy companies, while human rights groups argue it reduces corruption. Meanwhile, the gun rule requires extra scrutiny of purchasers who receive Social Security benefits and also have a history of mental illness. Liberal groups are outraged by the rollbacks, but their traditional allies, Democratic lawmakers, have limited means to stop them in the Republican-dominated Congress. Those on the Rules Committee said important protections were being rushed to the chopping block and pleaded for hearings on the regulations, to no avail. This week House Democrats and activists are planning to rally the public, hoping to persuade Republicans to vote no. Senate Democrats cannot filibuster the measures but congressional aides expect them to slow the process by taking the full five hours they are allowed to speak against each measure on the chamber’s floor. 