BEIRUT (Reuters) - A boat with 39 Syrian refugees aboard sank off the coast of Lebanon as it sailed illegally for Cyprus on Saturday and most were rescued by the Lebanese army but a five-year-old boy drowned, security sources said.

They said it appeared to be the first time in almost a year that a group of refugees had tried to get to Europe by boat from Lebanon, where Syrian refugees account for roughly a quarter of the population.

Cyprus is around 180 km (110 miles) from the coast of northern Lebanon. Three more of the people on the boat were in a serious condition in hospital, the sources said.

The U.N. refugee agency UNHCR says there are close to 1 million registered Syrian refugees in Lebanon. The Lebanese government puts the number at 1.5 million.

As Syrian forces and their allies have retaken more territory in Syria, Lebanon’s president and other politicians have called for refugees to go back to areas where fighting is over before a deal is reached to end the civil war.

Some refugees have trickled back to Syria in recent months in what the Lebanese authorities have described as voluntary returns coordinated with the Syrian government.

But U.N. High Commissioner for Refugees Filippo Grandi said during a visit to Beirut last month that refugees were concerned about issues including the lack of infrastructure and fear of retribution and military conscription.

For larger numbers to decide to go back, he said, more confidence must be created by addressing these issues and UNHCR should have a presence in areas of return, according to a statement on UNHCR’s website.