CONCORD, N.H. -- Democratic presidential candidate Pete Buttigieg was interrupted by environmental activists during a New Hampshire campaign event Friday, prompting him to confront the sign-wielding rabble-rousers as they accused him of taking money from "fossil fuel billionaires."

The brief demonstration -- which apparently included a group that backs rival candidate Sen. Bernie Sanders as well as a volunteer for Sen. Elizabeth Warren -- took place minutes after the former South Bend, Ind., mayor was formally endorsed by Rep. Annie Kuster, the first member of New Hampshire’s all-Democratic congressional delegation to back a candidate in the race for the party’s presidential nomination.

WHERE DOES PETE BUTTIGIEG STAND ON THE ISSUES?

The protesters – who said they were with a group called the New Hampshire Youth Movement – held up signs that read “Pete takes money from fossil fuel billionaires” and chanted, “We are fighting for our future and together we are strong.”

During the demonstration, Buttigieg said: "I see some inaccurate information going up here" and spotlighted that he had signed the pledge not to accept campaign contributions from the fossil fuel industry.

“I took the fossil-fuel pledge,” he said. The pledge has been signed by nearly the entire field of current and former Democratic presidential contenders.

And highlighting his battle to combat climate change, he told the demonstrators, “We want the same things.”

The group also protested former Vice President Joe Biden at a campaign event he held in Manchester, N.H., in October.

Griffin Sinclair Wingate, a spokesperson for the group, told Fox News, "We are really concerned about candidates who have taken money from fossil-fuel executives. So that includes Joe Biden as well as Pete Buttigieg."

"Pete Buttigieg hosted a fundraiser in a wine cellar or wine cave with Craig Hall, who runs a firm that funds fossil fuel infrastructure projects. As a young person who's really concerned about climate change and knows that our lives are threatened by the climate crisis, we cannot have a president who is taking money from fossil-fuel executives,” Wingate argued.

That ‘wine cave’ fundraiser grabbed national attention when a 2020 rival – Sen. Warren of Massachusetts – slammed Buttigieg over the event as the two candidates battled during December’s prime time debate.

Asked by Fox News about the group’s complaints, Buttigieg said: "My reaction is that I have a climate policy that's going to get us carbon neutral by the middle of the century and starts on Day One with aggressive action. And this is personal for me. As the youngest candidate running for president, I will be personally impacted by America's success or failure dealing with the climate issue.”

He added, “I respect the issues that they're raising. I share the goal of making sure that we deal with this and I'm going to do everything in my power to make sure that we can. One thing that we also know is that we're going up against a president who's pulling out all of the stops to remain in power and to block any meaningful action against climate change. We can't go into that fight with a hand tied behind our back.”

Buttigieg’s New Hampshire communications director Kevin Donohoe told Fox News, “We do not accept contributions from registered federal lobbyists, corporate PACs or the fossil fuel industry -- and the only promise any donor will ever get from Pete is that he will use their donations to defeat Donald Trump.”

Rights & Democracy NH, a group that backs Sanders, later said that some of their organizers were involved in the protest.

Following the demonstration, a Massachusetts college campus organizer who volunteered for Warren also took to Twitter to say she was part of that protest.

The Warren campaign told Fox News the woman had indeed volunteered for the campaign in New Hampshire this past summer.

Buttigieg was introduced by Kuster, the four-term representative who represents the state’s second congressional district.

Kuster compared Buttigieg to former President Barack Obama – whom Kuster campaigned for in the 2008 White House election.

“Like Barack Obama before him, he is young, he is inspiring, he brings fresh ideas to the table, and he is motivated to win this election,” Kuster told the crowd.

And Kuster appeared to take an indirect jab at two of Buttigieg’s top-tier rivals for the nomination – Sens. Sanders of Vermont and Warren.

“We have Democratic candidates in the Iowa caucuses who are tearing each down rather than lifting our country up with a strong coalition of interests and ideas,” she said.

Buttigieg was the longest of long-shots when he declared his candidacy a year ago. But he quickly started to soar in the polls and enjoyed a surge in fundraising in the spring and the summer. He made another jump in October and November, joining former Vice President Joe Biden and Sanders and Warren as part of the top tier of candidates in polls in New Hampshire and Iowa, which hold the first contests in the nominating calendar.

But he’s seen some slippage in his support in many recent surveys in both states. So with the Iowa and New Hampshire contents just weeks away, the endorsement of Kuster as well as the backing on Sunday from longtime Rep. Dave Loebsack of Iowa come at a very opportune time.

Buttigieg still struggles to gain traction with African-American voters – who will have a very influential role in South Carolina's late February primary, as well as in the Super Tuesday states in early March. That means strong finishes in both Iowa and New Hampshire are critical for Buttigieg as he battles for the Democratic nomination.