The ancient custom of lighting bonfires on Lag Ba'Omer is being challenged for both religious and ecological reasons.

The tradition of lighting bonfires on the eve of Lag Ba'Omer, which falls on Sunday, has become a popular custom in Israel, for religious and secular youngsters alike. But the prevalence of the custom, which causes large clouds of thick smoke above most Israeli citiesm, is raising concern amongst rabbis and environmentalists.

The Chief Rabbinate called upon the public last week to postpone the bonfires from Saturday night to Sunday, citing fears that many children would begin preparing the piles of wood and lighting them before Shabbat goes out. They also asked the Education Ministry to postpone the school holiday from Sunday to Monday but ministry sources explained that it was too late to change the school calendar.

The main Lag Ba'Omer celebrations on Mount Meron, at the grave of Rabbi Shimon Bar Yochai, will kick off only at 10PM to prevent any work on Shabbat. In the past, senior rabbis have also issued rulings against using wood from building sites and taking supermarket trolleys to transport the wood, saying that there was no excuse for theft in observing the ancient custom.

Meanwhile, the local council in Ra'anana, which bills itself as Israel's "green city", has asked parents to prevent their children from lighting bonfires, especially near residential areas, for environmental reasons.

Mayor Nachum Hofri wrote to parents that "I know this is not an easy request but I am asking you to cooperate so there will be no bonfires and that we find another way to mark the day. At the very least, minimise the number of bonfires by lighting a central one."

Other local councils, like Eilat, already have bylaws forbidding bonfires in parks and on beaches.