Belgium boss Roberto Martinez has said that his decision to leave Radja Nainggolan out of his World Cup squad is down to "tactical" reasons.

The 30-year-old is regarded as one of his nation's best players, and has enjoyed an impressive four-and-a-half-year period with Roma.

However, Nainggolan is the surprise exclusion in Martinez's provisional 28-man group, with the Spaniard suggesting that the player does not fit his style of play.

At a press conference, Martinez told reporters: "First and foremost, we all know Radja is a top player, there is no question about that. It is a tactical reason. In the last two years, the team has worked in an offensive way, in a very specific manner.

"In the case of Radja, we all know he has a very important role at club level and I don't think we can give him that in the national team.

"I travelled to see him yesterday in Rome and we had a very good conversation. The decision is not an easy one, I understand how popular the player is, but we have to create the team to try to become a winning team. It is purely a tactical decision."

Despite their contributions in the Premier League, both West Bromwich Albion midfielder Nacer Chadli and Crystal Palace forward Christian Benteke are both included, although Martinez must reduce his squad by five players before the start of the tournament.

Full squad

Goalkeepers: Koen Casteels (Wolfsburg), Thibaut Courtois (Chelsea), Simon Mignolet (Liverpool), Matz Sels (Newcastle United)

Defenders: Toby Alderweireld (Tottenham Hotspur), Dedryck Boyata (Celtic), Laurent Ciman (Los Angeles FC), Christian Kabasele (Watford), Vincent Kompany (Manchester City), Jordan Lukaku (Lazio), Thomas Meunier (Paris Saint-Germain), Thomas Vermaelen (Barcelona), Jan Vertonghen (Tottenham Hotspur)

Midfielders: Nacer Chadli (West Bromwich Albion), Kevin De Bruyne (Manchester City), Mousa Dembele (Tottenham Hotspur), Leander Dendoncker (Anderlecht), Marouane Fellaini (Manchester United), Youri Tielemans (Monaco), Axel Witsel (Tianjin Quanjian)

Forwards: Michy Batshuayi (Chelsea), Christian Benteke (Crystal Palace), Yannick Carrasco (Dalian Yifang), Eden Hazard (Chelsea), Thorgan Hazard (Borussia Monchengladbach), Adnan Januzaj (Real Sociedad), Romelu Lukaku (Manchester United), Dries Mertens (Napoli)