France has mobilized additional 1600 police officers, gendarmes to ensure security following the Brussels attacks.
"Europe is in a state of war. The terror threat remains on the highest level," Valls said at a government meeting.
Earlier France has closed its border with Belgium.
All EU institutions are at alert level ORANGE — all meetings on premises and outside cancelled, access only for staff with badges— Kristalina Georgieva (@KGeorgievaEU) 22 March 2016
Belgian intelligence had advance knowledge of plans to carry out terrorist attacks in the country but was unaware of their time or location, the French BFMTV reported Tuesday, citing police sources.
The blasts in Brussels come just days after Salah Abdeslam, the mastermind behind the November Paris Attacks, was arrested in Belgium.
At least 15 people have been killed in the Metro terror attacks in Brussels, according to Belgian broadcaster RTBF. Ten more people have been reportedly injured.