NEW YORK - Taliban militants came back to fight, slowing the advance of US-led NATO assault force into Helmand province Tuesday as improvised explosive devices in the region caused problems, according to reports in US media. International and Afghan forces descended on what is being described as the Taliban stronghold on Friday. The offensive was billed as the largest Afghan operation since U.S.-led forces overthrew the Taliban regime in 2001. Afghan Defence Minister Gen. Abdul Wardak was quoted as saying the aim of the operation is not to kill insurgents but to provide a stable environment for development. He called on insurgents to lay down their weapons and join the reconciliation process under way in the country. Afghan President Hamid Karzai announced a sweeping reintegration plan in the wake of a January conference for his country. Meanwhile, U.S. missile strikes killed three civilians Tuesday after weekend attacks left more than 12 dead, half of which were children, The New York Times said. British military authorities said most of the Taliban insurgency evaporated ahead of the offensive, though reports adds the advance of international forces was slowed to "a crawl" as insurgents resumed their fight.