The United States-led coalition carried out airstrikes in the Raqqa province in Syria early on Saturday, targeting strongholds of the Islamic State group, officials from the Syrian Observatory of the Human Rights said.

“Massive explosions” were reported in 31 locations around the al-Raqqa city as training camps and hideouts of the Islamic State group, formerly known as ISIS, were hit. Several attacks targeted the Tabqa air base, which militants of the Islamic State group had seized from the Syrian military in August.

Targets in the west Syrian city of Homs were hit for the first time Saturday, the Syrian Observatory for Human Rights reported, adding that the U.S.-led coalition had also carried out overnight airstrikes in the town of Minbej, east of Aleppo.

Observatory director Rami Abdel Rahman told The Daily Star that the targets struck in the Homs province were far away from where forces loyal to President Bashar Assad -- who control Homs city -- are positioned.

In the north, the coalition launched four air strikes on fighters of the Islamic State group east of the Kurdish-dominated city of Kobane near the Turkish border, according to an Al Jazeera report. ISIS militants have, over the recent weeks, laid siege to Kobane, forcing nearly 160,000 residents -- mostly Kurds fearing a repeat of the atrocities against the Yazidi community in northern Iraq -- to flee across the border to Turkey.

Clashes between Kurdish forces and Islamic State group fighters are still continuing near Kobane, according to media reports.

Nearly 40 nations, including several from the Middle East, have joined the US-led coalition against the Islamic State group.

Denmark, Belgium and the United Kingdom also joined the coalition on Friday. However, the European nations have refused to conduct airstrikes in Syria, committing to restrict their military action to ISIS strongholds in Iraq.