The US military said it fired on Iranian forces and sank six small boats targeting civilian ships as it moved to reopen the Strait of Hormuz on Monday, while the United Arab Emirates said it had come under attack from Iran for the first time since a fragile ceasefire took hold in early April. France 24's correspondent in Tehran, Reza Sayah, says tensions in the Middle East are at the highest they've been since the ceasefire began.