A rocket hit a base in northern Iraq that hosts US forces on Thursday but caused no casualties, Iraqi security sources said. The base, known as K1 near the city of Kirkuk, is where a US civilian contractor was killed in December in a similar attack, blamed by Washington on Iran-backed militias. A Reuters witness said US warplanes had scrambled and were soaring overhead shortly after the attack on Thursday. The December attack was followed by retaliatory US strikes that killed some two-dozen militiamen, attacks by crowds on the US embassy in Baghdad and then the killing by US drone strike in Baghdad of Iran’s Quds Force commander Qassem Soleimani. Followers of Soleimani and deputy leader of the Popular Mobilization Forces Abu Mahdi al-Muhandis, who died in the same strike, this week marked 40 days since the deaths of their leaders with ceremonies in Baghdad.