Belgian police have received an anti-terror alert warning that a group of Islamic State fighters recently left Syria en route for Europe planning attacks in Belgium and France, a security source said on Wednesday.The Belgian crisis centre in charge or coordinating security responses said that an alert had been circulated to all police forces in the country but there were no immediate plans to raise the security level to the maximum that would indicate an imminent threat of an attack.Newspaper DH quoted the alert from Belgium's anti-terror cell as saying the group "left Syria about a week and a half ago to reach Europe via Turkey and Greece by boat without passports", without giving an exact departure date.The alert came two days after an attacker who pledged allegiance to Islamic State killed a French police commander and his partner at their home outside Paris, and four days after a gunman declaring loyalty to the Islamist militant group massacred 49 people in a gay nightclub in Orlando, Florida.