As questions about the efficiency of Belgian security forces proliferate in the days after terrorist attacks Friday night gripped Paris in terror, the country announced that it would deploy as many as 300 more soldiers in Brussels and other major cities to provide support Tuesday. The announcement is a response to a raised threat level and gives police leeway to take on additional responsibilities, according to the Associated Press.

Those added troops mean that as many as 520 military personnel have been sent to the streets of Belgium in response to the attacks, which killed at least 129 at the start of the weekend. There has been a series of raids in France and Belgium following the attacks to find and arrest those involved in the planning and execution of the coordinated shootings and bombings, the AP reported.

In France Monday, leaders vowed to hunt down all Islamic State group militants in the country, and investigators said the planning behind the attacks, for which the group claimed responsibility, led all the way to Syria. French President François Hollande called a historic meeting of both of the French legislative chambers to say that the nation would be relentless and unforgiving in an attack campaign against the extremist group in Syria and that France was at war. Some of those involved in the attacks were previously known to security forces in the region.

Raids have led to at least 20 arrests in France and Belgium since the attacks, and some weapons have been seized in the process. Authorities are hoping to locate 28-year-old Abdelhamid Abaaoud, a Belgian of Moroccan descent, who they believe coordinated the Paris attacks. He has also been linked to other attacks, including the failed shooting attempt on a train traveling to Paris in August.

Abaaoud was believed to be plotting attacks from Syria.