Strikes by airport and airline staff grounded hundreds of flights and left thousands of travelers stranded in Europe on Saturday at the peak of the busy summer tourism season.

In Italy, some 1,000 flights, both domestic and international, were canceled as a result of the strike by ground crew, airport and airline authorities reported.

Another 120 flights due to depart and arrive from Belgium's Charleroi airport were canceled Saturday and Sunday, due to a walkout of budget carrier Ryanair pilots over working conditions.

Italy's strike alone left some 250,000 travelers stranded in one of the world's top tourist spots.

It comes amid a record heatwave, classified by the national weather service as "one of the most intense of all time," which would bring temperatures of at least 40 degrees Celsius (104 Fahrenheit) to Rome and 48°C to the islands of Sicily and Sardinia.

The strike by the ground crew, who are demanding a new collective contract six years after the previous one expired, was due to last from 10:00 am (0800 GMT) to 6:00 pm (1600 GMT).

The airport in Rome saw some 200 flights canceled, authorities said.

Flights by Malta Air, which handles transfers for popular budget carriers Ryanair, Vueling, and Ita Airways, were also affected after pilots joined the walkout. 

Milan's airports saw some 150 flight cancellations, while dozens of others were grounded in Turin and Palermo.

Italian Transport Minister Matteo Salvini called the strikers to exercise "common sense" so as "not to harm millions of other workers and tourists."

Read more: 950 Gatwick Airport employees to strike on July 28 over low wages