Ukraine crisis and sanctions on Russia
Pro-Russian protesters take part in a rally near the seized office of the SBU state security service in Luhansk, eastern UkraineReuters

The United States and European Union are set to widen their sanctions against Russia in response to Moscow's actions in the ongoing crisis in Ukraine.

EU diplomats are set to discuss further measures against Moscow and are likely to crack down on at least 15 Russian officials who are connected with Ukrainian affairs.

The sanctions, which are to be targeted at Russian President Vladimir Putin's inner circle, are to include travel bans and asset freezes. The US has not said exactly how many individuals will be targeted in the latest round of sanctions.

"There are lots of things that are going on around him, people who are around him, who matter to him, who are going to be affected by these sanctions," White House Deputy National Security Adviser Tony Blinken told CNN.

The US and the EU have already blacklisted 60 Ukrainian and Russian officials, including Putin's associates, since the unrest broke out in Ukraine. So far, the sanctions have failed to stop Russia from pressing ahead with its actions in Ukraine.

Foreign Secretary William Hague told Sky News: "The more names we add to that list the more they do bite in the Russian economy. But we are also working on more far-reaching measures of economic, trade and financial sanctions."

The EU is also preparing for broader sanctions to pile more pressure on certain key sectors of the Russian economy.

However, some European nations fear that such sanctions on Russia would affect their economies as well.

Meanwhile, in Ukraine, the pro-Russian separatists have released one of the eight captured foreign observers in the eastern city of Slavyansk.

The masked, heavily armed anti-Ukraine rebels captured the uniformed European monitors sent on behalf of the Organisation for Security and Cooperation in Europe (OSCE) three days ago in the flashpoint city.

German Foreign Minister Frank Walter Steinmeier said in a statement: "The public parading of the OSCE observers and Ukrainian security forces as prisoners is revolting and blatantly hurts the dignity of the victims."