DAKAR, SENEGAL--A Daesh offshoot is claiming it carried out the attack in Niger that killed four U.S. soldiers and four Nigerien troops in October and sparked questions about U.S. military involvement in West Africa's vast Sahel region. The news agency has carried messages from the affiliate before, according to the SITE Intelligence Group, which monitors jihadist websites. U.S. officials have said the joint U.S.-Niger patrol had been asked to assist a second American commando team hunting for a senior Daesh member. After completing that mission, the troops stopped in a village to get food and water, then left. Officials have pointed out the danger and difficulty of hunting down an enemy in region the size of Europe.