April 3 (Reuters) - Romania's financial supervision authority ASF
* Says assets held by Romania's mandatory private pension funds rose to 31.5 billion lei ($7.38 billion) in 2016, up 27.5 percent on the year.
* The European Union member overhauled its communist-era pension system in 2008, making it compulsory for working Romanians under 35 to contribute to a "second pillar" of private pension schemes as well as their state pension.
* Says 6.8 million people contributed to mandatory private pension funds in 2016.
* Says overall private pension assets, including optional third-pillar funds, amounted to 4.4 percent of gross domestic product at the end of 2016. ($1 = 4.2663 lei) (Reporting by Luiza Ilie; Editing by Radu Marinas)