The State Department, through the US embassy in Bogota, said it was not aware of any specific threat to Americans but urged those in Colombia to boost their security precautions, noting a series of deadly bombings last week in the run-up to Thursday's anniversary that killed 12 people in the country's northwest.

"The FARC has historically conducted terrorist attacks, especially bombings against civilian and public security targets, around the date of this anniversary," the embassy said in a notice to US citizens in Colombia.

"This trend appears to be the case again this year, with several such bombings in recent days and more possible in the days to come," said the notice, a copy of which was provided to AFP in Washington by the State Department.

At least 12 people were killed and 110 injured in three bombings in the northwestern province of Antioquia between Thursday and Saturday, including one in a crowded discotheque in the town of Apartado, according to local authorities.

No one has taken responsibility for the blasts but Colombian officials have blamed them on the 17,000-strong FARC, whose rebellion was launched by Manuel Marulanda, whose nom de guerre was "Tirofijo," or "Sure Shot," on May 27, 1964, in southern Colombia.

Although the embassy said it had no information that US citizens or interests would be targetted by the FARC, it said Americans should "maintain a heightened level of vigilance and to continue practicing good security measures during this time to avoid becoming victims of a terrorist attack."

The FARC, the oldest and strongest left-wing guerrilla insurgency in Latin America, is one of three Colombian groups the State Department has designated a "foreign terrorist organization."

The leftist National Liberation Army (ELN) and the right-wing paramilitary United Self Defence Forces (AUC) are the others.

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