Washington, Jan 10 (IANS): The US State Department has issued a global travel alert for Americans after 12 people of a French satirical magazine were massacred by two gunmen in Paris.

The alert, which was updated for the first time in three months, warned Americans travelling in Europe, the Middle East, Africa that they could face a terror attack or even abduction, Xinhua reported.

According to the warning, the specific concern here lies with the Islamic State (IS), which may retaliate against US military strikes by "calling on supporters to attack foreigners wherever they are."

"Extremists may elect to use conventional or non-conventional weapons, and target both official and private interests," it said.

In addition, the global alert also pointed out that government facilities around the world are on heightened vigilance as well, and may "temporarily close or periodically suspend public services to assess their security posture."

Americans travelling abroad are encouraged to stay in contact with US embassies or consulates wherever they are staying, it added.

Meanwhile, US Federal Bureau of Investigation and Homeland Security Department jointly issued a bulletin to 18,000 local law enforcement departments across the country, urging local police and the public to watch out for increased terrorist activity.

French attackers showed a high degree of training and sophistication compared to other recent attacks on soft targets, the bulletin warned.

"We urge the public to remain vigilant and report suspicious activity to law enforcement," it said.

The offices of Charlie Hebdo magazine were attacked by two brothers - Cherif and Said Kouachi- Jan 7.

They killed 12 people including the chief editor.