Londoners react to the newsroom shooting in Paris.

By the hundreds, they gathered outside the National Gallery at Trafalgar Square.

A silent vigil -- for ten journalists and two police officers killed earlier when suspected Islamist militants attacked the satirical French weekly, Charlie Hebdo.

'I am Charlie', their signs read.

Their pens held up -- like swords.

(SOUNDBITE) (English) VIGIL ATTENDEE, SAYING:

"I think what shocks me the most is that it has actually happened in this day and age. That some men can just walk into a building and decimate a whole team."

Eleven people were also wounded in the attack, several critically.

Terrorism experts say the gunmen behaved like trained commandos, and that the assault was apparently well-planned.

Witnesses say the journalists had gathered for a weekly meeting and that the gunmen called out some of their victims by name.

Security in France is at its highest level and other governmen