City police said on their Twitter account that "a possible explosive device was found" by officers at the Sant Sebastià beach, around a kilometer (mile) from the city's famous Gothic quarter.
Spanish media were speculating that it could be an unexploded device remaining from World War II, but there was no confirmation of that.
Spanish radio station COPE reported the device was in the sea, about 40 meters (yards) off the coast.
A police bomb squad was heading to the scene, COPE said, quoting Spanish news agency Efe.
Police have established a security perimeter of 250 meters wide around the device off the Sant Sebastia beach, one of most popular beaches in Barcelona .
The beach was reportedly full of people when it was evacuated in the early afternoon, with temperatures close to 30 degrees Celsius (86 Fahrenheit).
Please click to read our informative text prepared pursuant to the Law on the Protection of Personal Data No. 6698 and to get information about the cookies used on our website in accordance with the relevant legislation.
6698 sayılı Kişisel Verilerin Korunması Kanunu uyarınca hazırlanmış aydınlatma metnimizi okumak ve sitemizde ilgili mevzuata uygun olarak kullanılan çerezlerle ilgili bilgi almak için lütfen tıklayınız.
