US-led coalition airstrikes pound IS areas in eastern Syria Syrian activists are reporting intense airstrikes on the last area held by the Islamic State group in the country's east where the extremists control has been shrinking over the past weeks

BEIRUT -- Syrian activists are reporting intense airstrikes on the last area held by the Islamic State group in the country's east where the extremists' control has been shrinking over the past weeks.

The Britain-based Syrian Observatory for Human Rights said Thursday the airstrikes hit the 15 square kilometers (5.8 square miles) controlled by IS in the eastern province of Deir el-Zour after U.S.-backed Kurdish-led fighters of the Syrian Democratic Forces scored gains in recent weeks.

Europe-based activist Omar Abu Layla of the DeirEzzor 24 monitoring group confirmed intense airstrikes are ongoing, adding that they were triggered by a counter-offensive carried out by IS during a strong fog.

The airstrikes came a day after a suicide attack carried by IS insurgents killed 19 people, including four Americans, in the northern town of Manbij.