Unidentified assailants killed a coalition soldier in Afghanistan while local troops destroyed a heroin laboratory after battling Taliban fighters guarding the facility, NATO said Monday. The heroin lab in restive Helmand province contained large amounts of opium-processing chemicals as well as weapons, insurgent propaganda and explosive materials, according to a statement from NATO's International Security Assistance Force. Afghan troops "defeated" Taliban fighters guarding the facility before destroying it on Sunday, the statement said, without saying if there were any casualties. Afghanistan accounts for more than 90 percent of the world's heroin supply, and a significant portion of the profits from the $3.1 billion trade are thought to flow to Taliban fighters who tax and protect poppy farmers and drug runners. Also Sunday, a soldier from the 37-nation strong security assistance force was killed by small arms fire during a foot patrol in eastern Afghanistan, the statement said. It did not identify the nationality of the dead solider or who the assailants were. Insurgent attacks on Afghan and Western troops are running at their highest level since US forces invaded the country in 2001 to oust the hard-line Islamic Taliban rulers, who had harbored al-Qaida leaders following the attacks on the United States on Sept. 11, 2001.