Olena Lukash told local media she would ask the National Security and Defense Council to introduce the measures.
Protesters seized the building in Kiev late on Sunday and set up barricades outside with bags of snow.
Unrest is spreading across Ukraine, with activists taking over municipal buildings in several towns and cities.
Buildings have come under attack even in eastern areas, which have traditionally had closer ties with Russia and where President Viktor Yanukovych has enjoyed strong support.
The crisis was sparked by the president’s decision not to sign a deal with the European Union, and has escalated with the deaths of four activists in recent days.
Correspondents say protesters entered the justice ministry building in the capital without resistance.
“The seizure of the Ministry of Justice is a symbolic act of the people of the uprising. Now, these authorities are stripped of justice,” one protester told reporters.
But Olena Lukash told Inter TV channel: “If the protesters do not leave the justice ministry building… I will ask the National Security and Defense Council of Ukraine to impose the state of emergency.”
The minister is an ally of President Viktor Yanukovych and involved in the ongoing negotiations between the government and protest leaders.
She said she would be “forced to turn to the Ukrainian president with a request to stop the negotiations unless the justice ministry building is vacated without delay and the negotiators are given a chance to find a peaceful solution to the conflict”.
Last week, the parliament of the Crimean Autonomous Republic – seen as a staunch supporter of Viktor Yanukovych – also urged the president to declare a state of emergency.
The government has previously insisted it would not resort to the army, a measure our correspondent says would likely further antagonize the protesters and worsen the violence.
The parliament is due to meet for an extraordinary session on Tuesday, but the speaker has previously said a state of emergency will not be under discussion.
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