Marco Rubio (left) and Donald Trump during the Fox Business Network Republican presidential in North Charleston, S.C., on Thursday, Jan. 14, 2016.(AP Photo/Rainier Ehrhardt)

MANCHESTER, N.H. --  Republican front-runner Donald Trump and Sen. Marco Rubio (R-Fla.) are questioning President Obama's visit to a mosque in a Baltimore suburb on Wednesday, where he preached religious tolerance, recognized the achievements of Muslim Americans and encouraged young Muslim Americans to feel accepted.

Trump, who has long slyly suggested that Obama is not a Christian, said on Fox News on Wednesday night that Obama might have visited the mosque because "maybe he feels comfortable there." Meanwhile, Rubio said at a town hall at a pub in New Hampshire that Obama's decision to give a speech at a mosque is yet another example of him dividing the country.

Trump was asked to share his thoughts on the Obama's mosque visit -- his first as president -- during an interview with Fox News's Greta Van Susteren.

"I don't have much thought, I think that we can go to lots of places. Right now, I don't know if he's -- maybe he feels comfortable there," Trump said. "We have a lot of problems in this country, Greta, there are a lot of places he can go, and he chose a mosque. I saw that just a little while ago, and so that's his decision, that's fine."

[Conservative suspicions of refugees grow]

This isn't the first time Trump has seemed to question the president's religion. Years ago, Trump joined some fellow Republicans in questioning if Obama was truly born in the United States. At a town hall in New Hampshire in September, a man in the audience said Muslims are a problem facing the country and "our current president is one" -- a comment that prompted Trump to laugh. In a speech to the Republican Jewish Coalition in December, Trump questioned why Obama doesn't use the phrase "radical Islamic terrorism" and commented: "There's something going on with him that we don't know about." At a rally in New Hampshire on Tuesday night, Trump described Obama climbing into Air Force One to celebrate Christmas "or whatever he celebrates" in Hawaii.

Following attacks in Paris and San Bernardino late last year, Trump has called for heavy surveillance of mosques and a temporary ban on allowing foreign Muslims to enter the United States. He also promised that as president he would kick all Syrian refugees -- most of whom are Muslim -- out of the country and not allow any more to enter.

[Donald Trump calls for a ban on Muslims entering the country]

Rubio's reaction to Obama's mosque visit came during a town hall meeting at a pub in Dover, N.H., on Wednesday evening. Rubio accused Obama of pitting Americans against one another “along ethnic lines and racial lines and economic lines and religious lines.” His comments were part of a meandering response to a question about what his management style would be like as president.

“I’m tired of being divided against each other for political reasons like this president’s done," Rubio said. "Always pitting people against each other. Always.”

“Look at today – he gave a speech at a mosque,” Rubio continued. “Oh, you know, basically implying that America is discriminating against Muslims. Of course there’s going to be discrimination in America of every kind. But the bigger issue is radical Islam. And by the way, radical Islam poses a threat to Muslims themselves.”

“But again, it’s this constant pitting people against each other -- that I can’t stand that. It’s hurting our country badly," Rubio said. "We can disagree on things, right? I’m a Dolphin fan, you’re a Patriot fan."