(VOVworld) – Countries are collaborating in the hunt for individuals behind the terrorist attacks in Paris and airstrikes targeting the Islamic State have been intensified in Iraq and Syria.

A French soldier stood guard at the Eiffel Tower Sunday, following a spate of deadly terror attacks across Paris on Friday, Nov. 13, 2015. Getty Images

Germany has arrested 5 people in Aachen, suspected of having links to the Paris attacks. In Belgium, police have arrested 2 people suspected of providing materials to the terrorists in Paris. Searching their houses, police found ammonium nitrate, a main principle of fertilizer that can be used to make explosive.

French police have listed more than 10,000 people suspected of being radicalized or potential security threats. According to police sources, the so-called "S-file" is updated daily to include individuals suspected of links to a terrorist movement or group. The "S" stands for the suspects' potential danger to the "security of the state." The list has 15 categories spanning football hooligans to battle-hardened jihadists returning from Iraq and Syria. The suspects come into the spotlight if they are arrested or subjected to a check, after which they remain on the radar of the intelligence services.

Identification of suspects and sharing of information has been enhanced among French and foreign intelligence agencies. French police say 3 groups of terrorists wearing suicide vests were involved in coordinated attacks in Paris last Friday.

The Director of the Russian Federal Security Service (FSB) has announced a reward of 50 million USD for information leading to whoever was behind the terrorist attack last week on a Russian commercial airliner.

While France and other EU countries intensify the hunt for terrorists behind the Paris carnage, IS has posted a message on Twitter threatening to attack London, Washington, and Rome and any other country involved in airstrikes against IS.

The US and its allies have vowed to step up their campaign against IS. The USS Harry S.Truman Carrier Strike Group departed early Monday to join the French Charles de Gaulle Carrier in fighting IS in Syria and Iraq. US-led airstrikes targeted IS bases and destroyed 116 IS fuel trucks in eastern Syria and IS tactical units in 7 cities in Iraq.

The UK government will add 2 billion pounds to the military budget for anti-terrorism operations and increase its intelligence staff 15% to about 15,000, the most since a terrorist attack in London in 2005.