BEIRUT (Reuters) - The Syrian air force carried out more than 200 air strikes around the country in the past 36 hours, a group monitoring the war said on Tuesday, a rapid increase in government raids as U.S.-led forces bomb Islamist insurgents elsewhere.

The intensified strikes by President Bashar al-Assad's forces will add to the fear among his opponents that the government is taking advantage of the U.S. raids on Islamic State to attack other foes, including opposition groups that Washington backs.

Analysts say the increase could be because the Syrian military wants to weaken rebel groups before they get training and equipment promised by the United States.

Since midnight on Sunday, the Syrian military carried out at least 210 raids, including barrel bombings, on provinces in the east, north and west of the country, the Britain-based Syrian Observatory for Human Rights said. It said there were many casualties but did not give an exact figure.

The military concentrated the strikes in the "western corridor" that stretches from the southwest up through Damascus towards the Mediterranean, according to the information from the Observatory, which says it gathers details from all sides of the conflict.

The air raids struck areas in the Hama, Daraa, Idlib, Aleppo and Quneitra provinces as well as the Damascus countryside, it said. It also hit the eastern Deir al-Zor province where U.S.-led forces have also been bombing Islamic State, the Observatory added.

Before the surge in Syrian air force raids, the military had carried out 12-20 raids a day, according to the Observatory.

Damascus has not raised objections to the U.S. bombing of Islamic State, which is mainly based in the east and north of the country, far from the most populous areas near Damascus and the Mediterranean coast.

The United States says it does not want to help Assad's government despite bombing Islamic State, an al Qaeda offshoot that has become one of the most powerful insurgent groups in the more than three-year conflict.

(Reporting by Sylvia Westall; Editing by Alison Williams)