Factbox - Security alert levels in Europe

(Reuters) - The Belgian government has imposed the highest state of alert on the capital as police hunt suspects in the Nov. 13 attacks on Paris and say there are threats to Brussels. Other European governments have also issued or restated security alerts, some of which are detailed below. BELGIUM Belgium raised the alert status for the region around its capital Brussels to four, the highest level, on Nov. 21, warning of a "serious and imminent" threat. The threat level for the whole country was raised to level three on Nov. 14, indicating "a possible or probable threat". BRITAIN Britain's terrorism threat level has been at "severe", the second-highest category of five, since August 2014. "Severe" means an attack is highly likely, according to the scale. Prime Minister David Cameron said on Nov. 14 the level would not change in light of the Paris attacks. DENMARK Danish police increased their security readiness on Nov. 18 to the second-highest of five levels, described as having leadership, personnel and necessary forces put on the ready in case of an incident. The alert level has risen three times since a radicalised Danish youth shot dead two people in Copenhagen in February. FRANCE Following the Paris attacks in which 130 people were killed, France declared a state of emergency that will extend for three months. It is the first nationwide state of emergency since 1961, during the Algerian war of independence from France, although a state of emergency limited to the Paris region was declared during the suburban riots of 2005. The state of emergency allows broader powers of surveillance and arrest and makes it easier to take other steps such as banning marches and other gatherings. Ile de France, the greater Paris region, has been on the highest security alert status of five - "scarlet" - since 12 people were killed in an attack on the offices of satirical magazine Charlie Hebdo in January. GERMANY Germany has no formal levels of security alert. The day after the Paris attacks, Interior Minister Thomas de Maiziere said: "Germany remains in the cross-hairs of international terrorism ... the situation is serious. But I don't want to introduce any grades." In 2010, he issued a terror warning based on concrete intelligence indicating an attack on the Reichstag parliament building. "If such a situation is necessary, I would do it again," he said on Nov. 14. ITALY Italy has raised its alert level to two, one step below the maximum and the highest it can go without a direct attack. This allows a rapid deployment of special police and military forces if there is an emergency, according to the Interior Ministry. SPAIN Spain is currently at alert level four, or a "high risk of an attack", on an ascending scale of five. The level was raised on June 26 after attacks in France, Tunisia and Kuwait and the interior ministry said on Nov. 14 it was being kept there. SWEDEN Sweden raised its threat level by one notch - to four on a scale of five, the highest level ever assigned - on Nov. 18. Security police said that means there is a high probability that "persons have the intent and ability to carry out an attack". (Reporting by Reuters bureaux; Compiled by Catherine Evans; editing by David Stamp)