Belgrade, Sarajevo, Zagreb, Skopje - Two people have died and hundreds have sought medical assistance as a summer heat wave grips the western Balkans.

A period of extremely warm temperatures started as of this weekend and will last at least three weeks, meteorologists in the region said. They warned that temperatures - even above 40 degrees Celsius - may be set creating temperature highs not seen in the last 100 years.

To make the situation even more difficult for the population, this period will also be marked by so-called "tropical nights" where temperatures will remain above 20 or even 30 degrees Celsius overnight.

The first registered victim of the heat wave was a construction worker who collapsed and died in Zagreb on Monday. On the same day more than 700 people sought medical assistance in Zagreb and 500 in Sarajevo. A farmer near Bosnia's southern town of Mostar was also killed by the severe heat while working his land.

Medical workers warned the population to remain indoors between 11:00 and 17:00 and drink plenty of water.

The mercury in Serbia has topped 36 degrees Celsius over the past three days.

Despite the heat across the country, doctors from emergency centres have not reported any major incidents so far.

Nevertheless, their general advice to the public, especially to those with chronic diseases, is to stay indoors during the day and to wear light clothing.

The heat wave in Macedonia has led the national Crisis Management Centre there to warn of possible wildfires due to the tinder dry conditions.

Weather forecasts say rain is expected from late Tuesday onwards and this will slightly reduce temperatures.