Dozens of Ukrainian protesters took over the building Sunday night, smashing its windows, Agence France-Presse (AFP) reported.
Similar reports were posted by RT.com (Russia Today), and Kyivpost.com.
AFP said its correspondent reported protesters appeared to encounter no resistance.
It said they used trash containers to erect barricades outside the building.
Earlier Sunday, the Ukrainian opposition flatly rejected an offer from the president to share power following months of protests that turned deadly last week.
"No deal @ua_yanukovych, we're finishing what we started," tweeted opposition leader Arseniy Yatseniuk.
Ukrainian President Viktor Yanukovych met with leaders of the three main parliamentary opposition groups for the second time Saturday, offering the prime minister's post to Yatseniuk, leader of Batkivshchyna, the largest opposition party.
Former heavyweight boxer-turned-politician Vitali Klitschko was offered a job of deputy prime minister for humanitarian affairs.
After initially mulling the offers, and telling protesters gathered at Independence Square, "We are ready to take this responsibility and to lead Ukraine to European Union," Yatseniuk turned the post down, saying the president had not agreed to some key demands of the opposition including the calling of immediate elections, which are currently scheduled for next year.
"Negotiations will continue," Klitschko said.
The protesters led by the opposition also want amnesty for protesters, a change in the constitution to give more powers to parliament over the president, the repeal of a tough anti-protest law adopted Jan. 16 and the signing of a free trade agreement with the European Union.
The protests initially began Kiev on Nov. 21 in reaction to Yanukovych's rejection of the EU deal. On Jan. 19, they turned violent, after protesters attacked police blocking a street leading to parliament.
Police confirmed two deaths in the violence, but protesters say five were killed after police fired live ammunition at the crowds.
Since then, the protesters have occupied more than 11 governors' offices around the country as well an exhibition center in downtown Kiev with some 200 police officers inside.
Opposition leader Oleh Tyahnybok said the pressure has led Yanukovych to finally make concessions.
"Yanukovych talked to us only because you are here," Yatseniuk told the protesters.
Analysts say that Yanukovych, a wily and tough operator who has run Ukraine since 2010, realizes his position has been weakened.
"This offer shows that Yanukovych is worried about the strength of his main resource – law enforcement," said political analyst Taras Berezovets of Berta Communications in Kiev.
"It's not surrender but an attempt to play for time. He wants to split opposition leaders with this offer."
"But the opposition won't accept it – it would be silly to when the protesters already control half of the (outlying) regions and Yanukovych is as weak as ever," Berezovets added.
Protesters say they don't support such an offer and vowed to stay on the streets.
"It doesn't seem right to me – I joined the protest because I want Yanukovych to go, and so did most of the people here," said protester Tetyana Yakovenko, 41, in Kiev.
"I'm not sure people will agree to go home just because the opposition gets government positions."
On Tuesday, lawmakers will hold a special session of parliament that is intended to discuss a change in ministers and possibly repeal of the new anti-protest laws.
"Tuesday is judgment day," Yatseniuk told protesters.
"We don't believe what they say, we believe what they do."
Source: USA Today