The United Nations says more than 48,000 people have been forced to flee the Idlib and northern Aleppo areas in Syria as fighting between government forces and rebels escalates.

The UN Office for the Coordination of Humanitarian Affairs said more than half of the displaced are children. The attacks affected key infrastructure, including health facilities, schools and displacement camps.

The Syrian Observatory for Human Rights said the government forces carried out at least 45 airstrikes against rebel forces in northern Hama on Monday, the biggest attacks since last Wednesday. Hama province includes a strategic transportation hub that connects areas with the capital Damascus.

A Syrian state-run news agency reported that airstrikes also hit Idlib, causing several dozen casualties on the rebel side.

More than 510 people, including civilians, have reportedly died in the hostilities since last week.