Pakistan, June 17 -- Protesters used water pistols against unsuspecting tourists in Barcelona and on the Spanish island of Mallorca on Sunday as demonstrators marched to demand a rethink of an economic model they believe is fueling a housing crunch and erasing the character of their hometowns.

The marches were part of the first coordinated effort by activists concerned with the ills of overtourism across southern Europe's top destinations. While several thousands rallied in Mallorca in the biggest gathering of the day, hundreds more gathered in other Spanish cities, as well as in Venice, Italy, and Portugal's capital, Lisbon.

"The squirt guns are to bother the tourists a bit," Andreu Martinez said in Barcelona with a chuckle after sprit...