QUEBEC CITY - Four protesters who managed to infiltrate the building that houses the office of Quebec Premier Jean Charest left after occupying it for several hours Monday.

The Greenpeace activists were protesting against nuclear power.

They chained themselves up inside the Honore Mercier building by the legislature, which holds the premier's office. Charest was far away from the incident Tuesday, as he was delivering a speech in Toronto.

The four protesters were asked by security guards to remove their chains and they were escorted out of the building around noon.

A Greenpeace spokesman said they face charges of disturbing the peace, obstruction, unlawful access to a public building and illegal assembly.

The protesters spread their anti-nuclear message in advance of the one-year anniversary of Japan's earthquake, which prompted global fears of a catastrophe at the Fukushima plant. They unfurled a large yellow banner to remind people of the nuclear incident which began on March 11, 2011.

In Quebec, the provincial government is now deciding whether to refurbish the Gentilly nuclear facility, near Trois-Rivieres. The facility produces only a tiny fraction of Quebec's energy.

Greenpeace said the Gentilly plant is dangerous and should be closed this year.

The protesters noted that if it was so easy for them to penetrate the premier's office, how could the government possibility guarantee the safety standards of its the nuclear site.