Todd Akin, whose remarks on abortion and rape led fellow Republicans to urge him to quit as the party’s Senate candidate in Missouri, reiterated his vow to stay in the race as authorities investigate threats against him.

Akin, a six-term congressman, said today he will continue his campaign to unseat Democratic Sen. Claire McCaskill despite pressure to abandon his bid from Republican leaders, including presidential nominee Mitt Romney.

“There are some people who are having trouble understanding our message,” Akin said during a news conference in Chesterfield, Mo. “We’re going to be here through the November election and we’re going to be here to win.”

Akin, 65, stirred outrage from women’s groups and lawmakers in both parties after he said during an Aug. 19 interview that “legitimate rape” rarely leads to pregnancy. The controversy roiled a race that may be pivotal for control of the Senate just as Republicans prepare to hold their nominating convention next week in Tampa, Fla. He has since apologized, saying he “misspoke.”

Akin said today that there have been threats against him since his remarks. “There have been threats, both on life and on rape,” the lawmaker said, adding that House rules barred him from disclosing more.

Capitol Police and the Federal Bureau of Investigation are investigating “at least one threat they deem significant,” Steve Taylor, a member of Akin’s congressional staff in Missouri, said in a telephone interview yesterday. Capitol Police and Lauren Ellis, Akin’s chief of staff, also confirmed the investigation.

Taylor declined to specify the exact nature of the threat. Calls to the congressman’s office urged the “rape of Congressman Akin’s official staff, the congressman and members of his family, and there’s also been some suggestions that some people die,” Taylor said.

Capitol Police are working with the FBI “on a reported threat against Congressman Akin,” Lieutenant Kimberly Schneider said in an e-mailed statement. “This is an active, open investigation. Of course, we don’t discuss the security of members of Congress — this includes our security operations and procedures.”

The FBI didn’t respond to requests for comment.

Akin beat St. Louis businessman John Brunner and former State Treasurer Sarah Steelman in an Aug. 7 primary. In reiterating his intent to stay in the race today, Akin said: “That was the election, and I was the nominee.”

Akin faced down several calls from within his party’s leadership to leave the Senate race earlier this week, remaining past an Aug. 21 deadline to remove his name from the ballot.

“Todd Akin’s comments were offensive and wrong, and he should very seriously consider what course would be in the best interest of our country,” Republican presidential hopeful Mitt Romney said in a statement this week. Romney called for him to “exit the Senate race.”

The National Republican Senatorial Committee has said it would no longer help Akin. The U.S. Chamber of Commerce, which had previously funded ads against McCaskill, won’t continue to be involved in the race, a spokeswoman told the Associated Press.

Akin’s campaign tried to use opposition within the party to his advantage, saying in one fundraising appeal: “Party bosses have been clear: They want nothing to do with our effort to unseat liberal Claire McCaskill.”

Akin raised more than $100,000 in contributions in an appeal to donors this week, according to his campaign.