Serbian government monitors telephones to enforce travellers' quarantine

With more than 71,000 Serbian citizens returning to the country, primarily from Germany, Austria, Italy, and France, the government has introduced systems to ensure they obey the country's self-isolation rules. The government monitors telephone numbers, especially Italian ones, and pays special attention to communities with a large influx of people from elsewhere. 
https://advox.globalvoices.org/2020/03/30/covid-19-pandemic-adversely-affects-digital-rights-in-the-balkans/#

Source: https://mondo.rs/Info/Drustvo/a1298105/Aleksandar-Vucic-policija-telefonski-brojevi-policijski-sat-upozorenje-krecu-se.html

Writer: Advox; Mondo.rs
Publication: Global Voices; Mondo