Mark Halperin, a well-known Washington journalist and best-selling author, will no longer serve as an MSNBC contributor and NBC analyst following multiple allegations of sexual harassment.

"We find the story and the allegations very troubling," MSNBC said in a statement Thursday morning. "Mark Halperin is leaving his role as a contributor until the questions around his past conduct are fully understood."

The allegations come from five anonymous women during Halperin's time as a political director at ABC News more than a decade ago, and include claims that he allegedly grabbed a woman's breasts without consent and pressed a clothed erection against three of his coworkers.

"I went up to have a soda and talk and — he just kissed me and grabbed my boobs," a former ABC News employee told CNN's Oliver Darcy. "I just froze. I didn't know what to do."

In a statement to CNN, Halperin denied the specific allegations, but did admit that his conduct while a senior employee at ABC News was inappropriate.

"During this period, I did pursue relationships with women that I worked with, including some junior to me," Halperin said. "I now understand from these accounts that my behavior was inappropriate and caused others pain. For that, I am deeply sorry and I apologize. Under the circumstances, I'm going to take a step back from my day-to-day work while I properly deal with this situation."

After the allegations were reported, One America News Network senior political correspondent Emily Miller said she was also "attacked" by Halperin during her time as an ABC News associate producer.

"I did not report Halperin to ABC because I thought I was the only one, and I blamed myself, and I was embarrassed and I was scared of him," Miller wrote on Twitter.

In a statement, ABC News said no complaints were filed against Halperin during his tenure at the network. CNN senior correspondent Clarissa Ward said Thursday that the allegations against Halperin were an "open secret" during her three years as an ABC News correspondent.

"This was an open secret when I was at @ABC for years — brave of these women to speak up," Ward wrote on Twitter.

A solemn Mika Brzezinski, cohost of Morning Joe, addressed Halperin's absence on the show Thursday morning.

"Now to a story that broke overnight involving someone you see around this table every day. CNN is reporting allegations regarding our friend Mark Halperin during his time at ABC News over a decade ago, unnamed sources detailing unwanted advances and inappropriate behavior. Halperin apologized for the pain his actions caused and said, 'I will take a step back from my day-to-day work while I properly address the situation,' " Brzezinski said. "We are going to be following this story as it develops. I'm sure we are going to be talking about it again when we know more about it."

This isn't the first time Halperin has found himself at the center of controversy. In 2011, MSNBC suspended him after he called President  Barack Obama "a dick" on Morning Joe, a comment he later called "unacceptable."

Halperin is widely considered one of Washington's most prominent political journalists. He coauthored the best-selling book Game Change about the 2008 election, which HBO made into a movie with Julianne Moore starring as Sarah Palin. He is working on a new project with writing partner John Heilemann about Donald Trump's rise to the presidency. That project is also in development with HBO.