The Obama administration on Friday announced another round of sanctions against individuals supporting Russia's annexation of Ukraine's Crimean peninsula, also targeting an oil company that is based in the disputed region.

The Treasury Department's Office of Foreign Assets Control marked six Crimean “separatist leaders,” a former Ukrainian official and the Crimean-based gas company Chernomorneftegaz for sanctions.

In a statement, the Treasury Department said these individuals and entities had engaged in undermining democracy in Ukraine and the sovereignty of the country.

“As a result of Treasury’s action, any assets of the persons designated today that are within U.S. jurisdiction must be frozen. Additionally, transactions by U.S. persons or with the United States involving these individuals and entity are generally prohibited.”

According to a report, sanctions on Chernomorneftegaz could hamper efforts by Gazprom, a state-controlled Russian company, from bidding for the firm.

“Crimea is occupied territory. We will continue to impose costs on those involved in ongoing violations of Ukraine’s sovereignty and territorial integrity,” David S. Cohen, under secretary for Terrorism and Financial Intelligence, said in a statement.

The sanctions mark the third round of U.S. measures after Moscow annexed Crimea and comes as Russian President Vladimir Putin has rebuffed calls from President Obama and other world leaders to de-escalate the situation.

Putin has said that he has no intention of invading the rest of Ukraine, but has massed military forces along the country’s borders.

Tensions rose again this week after pro-Russian nationalists took over government buildings in one Ukrainian city and called for Moscow to protect them. The group was eventually removed by Ukrainian security forces.

The White House said it saw “increased Russian pressure” to stabilize the Ukrainian government. White House press secretary Jay Carney said there was “strong evidence” that many of those “demonstrators were paid and not local residents.”

The State Department on Friday also announced that Secretary of State John Kerry would be traveling to Geneva on April 17 to meet with Ukrainian, Russian and European Union officials about the situation in Ukraine.

“Secretary Kerry will continue efforts to deescalate the situation in Ukraine and find a diplomatic path forward,” State Department spokesperson Jen Psaki said in a statement. “The United States is committed to mobilizing the international community in support of Ukraine, and helping the Ukrainian people build the stable, democratic and prosperous country.”

The seven individuals designated for sanctions Friday are Crimean leaders Pyotr Zima, Aleksei Chaliy, Rustam Temirgaliev, Yuriy Zherebtsov, Mikhail Malyshev, and Valery Medvedev; and former Ukrainian official Sergei Tsekov.