Washington, May 5 (IANS): The 2016 Republican presidential nomination race has become crowded as two more candidates, retired neurosurgeon Ben Carson and former Hewlett-Packard CEO Carly Fiorina, Monday announced their candidacy for presidency.

Fiorina, 60, announced her White House bid on Monday morning on her twitter account with a campaign slogan "New Possibilities. Real Leadership" on top of her campaign website, reports Xinhua.

As the first and most likely the only female contender in the Republican presidential nomination, Fiorina in recent months has emerged as a vocal critic of the powerful Democratic presidential candidate, former US Secretary of State Hillary Clinton, as Clinton was grappling with controversies surrounding her State Department e-mail records and family foundation's acceptance of overseas donations.

"She clearly is not trustworthy, about a whole set of things," Fiorina told the US TV network ABC news on Monday morning. "She hasn't been transparent about her server and her emails, and now we see all of these foreign government donations to the Clinton Global Initiative."

Carson, an African-American conservative known for his criticism of US President Barack Obama's policies, also announced his plan to join the party's fast-growing field Sunday in interviews with US media. His official campaigning launch was held on Monday in his hometown of Detroit, the state of Michigan.

"I'm probably never going to be politically correct because I'm not a politician," he told supporters at his Monday campaign rally in Detroit. "I don't want to be a politician. Because politicians do what is politically expedient -- I want to do what's right."

Like Fiorina, Carson has never held public office before. The two are now joining three other GOP candidates -- Senators Ted Cruz, Rand Paul and Marco Rubio -- in a presidential nomination race that features younger and more diverse faces than in recent years.