New US sanctions target Russian officials and companies
The US has imposed sanctions on seven Russian individuals and 17 companies it says are linked to President Vladimir Putin's "inner circle".
The White House said the move was a response to "Russia's continued illegal intervention in Ukraine".
Those targeted include Igor Sechin, head of oil giant Rosneft, and Sergei Chemezov of the hi-tech firm Rostec.
The announcement comes after the mayor of Kharkiv, a city in eastern Ukraine, was shot and critically wounded.
Hennadiy Kernes was recovering after an operation to repair damage to the chest and abdomen, but his life remained in danger, his office said.
Mr Kernes used to be a supporter of former pro-Moscow President Viktor Yanukovych. He then dropped his support for Mr Yanukovych in favour of a united Ukraine.
Monday also saw pro-Russian separatists seize a local government building in Kostyantynivka, a town in the eastern Donetsk region.
In Donetsk itself, pro-Russian activists armed with clubs and chains attacked a pro-unity rally. A number of people were injured in the clash.
Western countries accuse Russia of actively supporting the activists in Eastern Ukraine - a claim denied by Moscow.
Separatists were also continuing to detain about 40 people in the town of Sloviansk, including journalists, pro-Kiev activists and seven military observers linked to the Organisation for Security and Co-operation in Europe (OSCE) as well as three members of Ukraine's security service, officials in Kiev said.
At an OSCE meeting in Vienna, Russian ambassador Andrei Kelin said Moscow was taking "steps" to secure the observers' release. But the area around Sloviansk was very tense and it had been "extremely irresponsible" to send them there, he added.
UN Secretary General Ban Ki-moon later called for the immediate and unconditional release of the observers.
Separately, Russian Defence Minister Sergei Shoigu in a phone call with his US counterpart Chuck Hagel said Russian troops had returned to their permanent positions after conducting military exercises on the border with Ukraine.
But he did not say whether the overall number of Russian troops deployed in the region - said to be around 40,000 - had been reduced.
Meanwhile, Mr Hagel warned that Russia's continued aggression would result in more diplomatic and economic pressure.
The US and EU first imposed visa bans and asset freezes on a number of senior Russian officials and companies after Moscow annexed Crimea from Ukraine last month.
On Thursday, the White House said it was adding to its sanctions list "in response to Russia's continued illegal intervention in Ukraine and provocative acts that undermine Ukraine's democracy".
It accused Russia of "doing nothing to meet the commitments it made" at a meeting with Ukraine, the US and EU in Geneva on 17 April, which it said had included refraining from violence or provocative acts.
Russian Deputy Foreign Minister Sergei Ryabkov said Moscow's response would be "painful for Washington".
He told the Interfax news agency the Kremlin was "disgusted" by the sanctions.
Among the seven government officials facing a US asset freeze and visa ban, two are seen as long-time allies:
- Mr Sechin is a former KGB officer and was deputy chief of staff during Mr Putin's first two presidential terms, when he masterminded Russia's energy policy
- Mr Chemezov is described by the US as a trusted ally dating back to the 1980s
- Alexei Pushkov is chairman of the committee of international affairs of Russia's lower house of parliament, the State Duma
Most of the 17 companies targeted are linked to Arkady and Boris Rotenberg and Gennady Timchenko - individuals targeted in the previous sanctions list.
The latest measures also targets some hi-tech exports that "could contribute to Russia's military capabilities".
Meanwhile, diplomats in Brussels said EU governments had reached a preliminary agreement to impose similar sanctions on another 15 people as part of expanded sanctions against Russia. The names are expected to be released on Tuesday.