Washington (CNN) The Trump administration announced Thursday it is enacting new sanctions on Russia, including individuals indicted last month by special counsel Robert Mueller , in a sweeping new effort to punish Moscow for its attempts to interfere in the 2016 US election.

In enacting the sanctions, the administration is finally meeting a congressional mandate to impose measures punishing Moscow for its cyber intrusion. The delay had led to questions over President Donald Trump's willingness to punish Moscow. The new measures, however delayed, amount to the most stringent punishment yet by Trump for Russia's election interference.

In announcing the measures, the administration also disclosed a Russian attempt to penetrate the US energy grid, and said the new sanctions would punish actors for their participation in other major cyberattacks.

The new punishments include sanctions on the Internet Research Agency, a Russian troll farm that produced divisive political posts on American social media platforms during the 2016 presidential election. Yevgeniy Viktorovich Prigozhin, a financial backer to the Internet Research Agency with deep ties to Russian President Vladimir Putin, is also included.

In addition to those included in Mueller's indictments, sanctions were slapped on two Russian intelligence agencies, the Federal Security Service and the Main Intelligence Directorate, as well as some of their employees.

The administration also accused Moscow of attempting to hack the US energy grid, a previously undisclosed claim that officials said was orchestrated by Russian intelligence.

"The administration is confronting and countering malign Russian cyber activity, including their attempted interference in US elections, destructive cyber-attacks, and intrusions targeting critical infrastructure," said Treasury Secretary Steven Mnuchin in a statement.

In total, the administration applied new sanctions on five entities and 19 individuals on Thursday, including Russians who posed as Americans and posted content online as part of the IRA's attempts to sow discord ahead of the presidential contest. They came as the US joined European allies in blaming Russia for a nerve agent attack in Britain, deeming the action a "clear violation" of international law.

During a meeting in the Oval Office on Thursday with the Irish Taoiseach, Trump told reporters that "it certainly looks like" the Russians were behind the nerve agent attack in the United Kingdom.

"It looks like it," Trump said. "I spoke with the Prime Minister and we are in deep discussions. A very sad situation."

"Something that should never ever happen, and we are taking it very seriously, as I think are many others," Trump said.

The new sanctions would bar the individuals from traveling to the United States, and freeze whatever assets they may have in the country.

The sanctions were applied through executive power as well as through the Countering America's Adversaries Through Sanctions Act, which Congress initially passed this summer hoping to pressure Trump into punishing Russia for its election interference.

Trump signed the bill reluctantly in August, claiming it impinged upon his executive powers and could dampen his attempts to improve ties with Moscow.

The measure imposed an October deadline on the administration to produce lists of individuals and entities that could be subject to potential sanctions and a January deadline to impose them. The law required the administration to identify entities that conduct significant business with the Russian defense and intelligence sectors.

The administration missed both by several weeks, claiming necessary work was underway at the State and Treasury Departments to complete the lists.

The delay was seen as sign of Trump's unwillingness to punish Russia for its meddling, which he has downplayed in the past. Members of Congress expressed frustration that their law, which passed almost unanimously, wasn't being enacted.

The White House said on Thursday that Russia had a decision to make as it moves forward.

"They are going to have to decide whether or not they want to be a good actor or a bad actor," press secretary Sarah Sanders said. "I think you can see from the actions we have taken up until this point we are going to be tough on Russia until they start to change their behavior."

On Thursday, administration officials insisted the new measures weren't the end of their efforts to punish Russia.

"By no means will this constitute the end to our ongoing campaign to instruct Mr. Putin to change his behavior," a senior administration official told reporters.