Belgian midfielder Radja Nainggolan called on Inter Milan to step up to play their part in Europe after his 38-million-euro transfer from Serie A rivals Roma was confirmed Tuesday.

The 30-year-old, who retired from international football after missing out on selection for Belgium's World Cup squad, signed a four-year contract.

"We can do well in the league and also in the Champions League. Inter have an important history behind them and they must now return to playing their part in Europe," said Nainggolan.

As part of the Belgian's move north, Roma welcome 18-year-old midfielder Nicolo Zaniolo and left-back Davide Santon, 27, on deals worth 4.5m and 9.5m euros respectively.