The FBI squarely blamed Russian intelligence services on Thursday for meddling in the 2016 U.S. presidential election, releasing the most definitive report yet on the issue, including samples of malicious computer code said to have been used in a broad hacking campaign.

Starting in mid-2015, Russia’s foreign intelligence agency, the FSB, emailed a malicious link to more than 1,000 recipients, including U.S. government targets, the Federal Bureau of Investigation said in a 13-page report co-authored with the Department of Homeland Security. (bit.ly/2iuT8cp)

While the Department of Homeland Security and Office of the Director of National Intelligence had said Russia was behind the hacking in October, the report is the first detailed technical analysis provided by the government and the first official FBI statement.

Russia has consistently denied the hacking allegations.

The FBI issued its report on the same day that President Barack Obama announced a series of retaliatory measures, including the expulsion of 35 Russian intelligence operatives and the sanctioning of the GRU and FSB. The Kremlin denounced the sanctions as unlawful and promised “adequate” retaliation.

According to the FBI report, among the groups compromised by the FSB hacks was the Democratic National Committee, which was again infiltrated in early 2016 by another Russian agency, the military GRU.

The report largely corroborates earlier findings from private cyber firms, such as CrowdStrike, which probed the hacks at the DNC and elsewhere, and is a preview of a more detailed assessment from the U.S. intelligence community that President Barack Obama ordered completed before he leaves office next month, a source familiar with the matter said.

Much of the information provided in the report is not new, the source said, reflecting the difficulty of publicly attributing cyber attacks without revealing classified sources and methods used by the government.

Some senior Republican leaders in the U.S. Congress have expressed outrage at what they called Russian interference in America’s elections, diverging from their own party’s president-elect. The allegations and sanctions mark a new post-Cold War low in U.S.-Russian ties.

Throughout the raucous campaign, a steady stream of leaked Democratic emails clouded the candidacy of party nominee Hillary Clinton. In the aftermath of her defeat, Democrats have accused Russia. Meantime, Trump, a Republican, has questioned whether Russia was truly at fault and told the Democrats to get over it.

“It’s time for our country to move on to bigger and better things,” Trump said in a statement on Thursday.

Trump has praised Russian President Vladimir Putin, tapped people seen as friendly to Moscow for administration posts and rejected assessments by intelligence agencies on the hacking.

The FBI said hackers gained access to and stole sensitive information, including internal emails “likely leading to the exfiltration of information from multiple senior party members” and public leaks of that information.

The report did not name hacked organizations or address previous conclusions reached by the Central Intelligence Agency and FBI, according to U.S. officials, that Russia sought to intervene in the election to help Trump defeat Clinton.

(Editing by Kevin Drawbaugh and Lisa Shumaker)