In the wake of the bombings in Belgium this week -- and increasing criticism of officials for their inability to thwart those attacks -- police in the last 24 hours have made at least four arrests in a series of raids in Belgium and four other countries across Europe.

New evidence shows disturbing evidence of just how big the terror network is across Europe.

CBS News' Allen Pizzey reports from Brussels that, as the effort to break the terrorist cell that carried out the bombings goes on, Belgian officials are coming under increased scrutiny and criticism for what is being seen as a series of intelligence failures.

In an operation that played out in full view, Belgian police shot a man who was spotted with a suspicious bag at a tram stop Friday.

Reuters/Vincent Kessler

Cell phone video taken by terrified eyewitnesses in an overlooking apartment shows police approaching and then a young girl stepping out of the tram stop shelter and being led to safety and then armed police move in.

The incident was one of three targeted raids in an area where earlier in the week police found a bomb-making factory they said was connected to the Brussels airport and subway attacks.

The raids have uncovered what is being described as "alarming" evidence of a Europe-wide jihadist cell connected to the attacks in Belgium as well as those in Paris in November.

Two brothers who died as suicide bombers in the attacks in Brussels last week were known to police as petty criminals and potential terrorists.

CBS

Ibrahim El Bakraoui, who blew himself up in the airport, had been arrested and deported from Turkey and labelled a "foreign terrorist fighter."

His brother Khalid, who died in the subway attack, was subject to an international arrest warrant after the Paris attacks.

Officials have told CBS News that the brothers were on the radar of U.S. law enforcement.

DNA found on a suicide vest and a piece of cloth at the Bataclan concert hall massacre in Paris and a bomb at the Stade de France stadium was that of Brussels airport bomber Najim Laachraoui.

In a stark contrast to other places where jihadi terrorists have struck, there has been no militaristic flag-waving in Brussels and no real backlash against Muslims.

Carl Court/Getty Images

As the Belgian prime minister put it in a speech to Parliament, "freedom ... the rule of law and tolerance are more than ever our reference points for moving forward together."

But moving forward is a slow process. With a manhunt on for at least two missing suspects, the authorities announced that Brussels' airport won't open before Tuesday at the earliest.