U.S. investigators believe Iran, or groups backed by Iran, are behind attacks on four oil tankers in the Persian Gulf region. The location is near a sea lane critical to the world’s supply of oil, and the incidents coincide with a surge in U.S.-Iranian tensions after the United States said last week that it has received intelligence that Iran was planning some kind of attack on U.S. forces in the Middle East. In response to the threat, the Pentagon dispatched reinforcements to the Persian Gulf, including an aircraft carrier, a Patriot missile battery and a squadron of B-52 bombers. The moves prompted Iran to warn that it is prepared to retaliate if it is attacked. Iran’s Foreign Ministry denied involvement in the attacks, condemned the actions as “alarming and regrettable” and said it would have a “negative effect” on shipping safety and maritime security, according to the Iranian Students’ News Agency.