Protesters in Bangkok are not giving up in their bid to overthrow Prime Minister Yingluck Shinawatra.

Since early this week, protest leaders have called on them to occupy key government offices.

On Saturday, thousands rallied towards the Department of Special Investigations, forcing their way into the compound.

Throughout the demonstrations, protesters have been blowing whistles to symbolise their frustration

Later they trooped to the office of the state-owned telecommunications company.

The prime minister said adequate security measures were in place, and appealed to protesters to return to negotiations.

(SOUNDBITE) (Thai) YINGLUCK SHINAWATRA, THAI PRIME MINISTER SAYING:

"This government chose to be called weak and has tried to avoid violence rather than put down a deadline and ask for the areas (overtaken by protesters) to be given back through violence. This would only hurt the people."

The protesters are accusing Yingluck of pushing f