Washington, Jan 12 : President Joe Biden has said that he ordered the strikes "in direct response to unprecedented Houthi attacks against international maritime vessels in the Red Sea" as quoted by media reports. A US-led coalition struck Iran-aligned Houthi militants in Yemen on Thursday, a dramatic escalation after the group ignored warnings from the Biden administration and other governments to stop attacking commercial vessels in the Red Sea, CNN reported. In a statement on Thursday, President Biden characterised the strikes as a necessary response to the pattern of violence that has affected several countries, saying they were directed at "a number of targets" used by the Houthis to launch their attacks. He did not disclose whether anyone had been killed in the operation. "These attacks have endangered US personnel, civilian mariners, and our partners, jeopardised trade, and threatened freedom of navigation," he said as quoted by CNN report. Biden added that he will "not hesitate to direct further measures to protect our people and the free flow of international commerce as necessary". Senior US officials have blamed Iran for having "aided and abetted" the crisis in the Red Sea, saying the Houthis would be incapable of threatening the shipping route if not for Tehran's technological and intelligence support. "Today, at my direction, US military forces--together with the UK and with support from Australia, Bahrain, Canada, and the Netherlands--successfully conducted strikes against a number of targets in Yemen used by Houthi rebels to endanger freedom of navigation in one of the world's most vital waterways," President Biden said in a statement released by the White House as quoted by CNN report. The strikes were from fighter jets and Tomahawk missiles. More than a dozen Houthi targets were fired upon by missiles fired from air, surface, and sub platforms and were chosen for their ability to degrade the Houthis' continued attacks on vessels in the Red Sea, a US official told CNN. They included radar systems, drone storage and launch sites, ballistic missile storage and launch sites, and cruise missile storage and launch sites. The strikes are a sign of the growing international alarm over the threat to one of the world's most critical waterways. For weeks, the US had sought to avoid direct strikes on Yemen because of the risk of escalation in a region already simmering with tension, but the ongoing Houthi attacks on international shipping compelled the coalition to act. /IANS