Republican presidential nominee Donald Trump has accused the Obama administration of waging a 'politically correct' war against ISIS and warned that more terror attacks will take place.

"We're not taking it to them," Trump told Fox News' Sean Hannity at a Wisconsin town hall. "And we have to take it to them."

Trump reiterated his call for "extreme" vetting of would-be immigrants to the United States, saying, "We are just allowing people into our country that some are going to be a problem. And we have enough problems in our country right now."

"We can be nice about it, say it's never going to happen again, there will be more [attacks]," Trump later added. "What we're doing by allowing tens of thousands of people in ... we don't know anything about, it's going to happen again because there's something wrong, and until we figure it out, we have to stop it."

Trump appeared with Hannity at a town hall at Milwaukee's Pabst Theater. The program was recorded Tuesday and aired Wednesday night.

Trump criticized the Obama administration for completing the withdrawal of U.S. troops from Iraq in 2011, which he called "ridiculous" and "absolutely insane." He also hit his Democratic rival Hillary Clinton for backing U.S. intervention in Libya during her tenure as secretary of state.

"We did the stupid attacks on Libya and got nothing out of it," Trump said, "and ISIS has taken over the oil and it's some of the finest oil in the world." 

At one point, Trump was joined on stage by survivors of three terror attacks that took place during the Obama administration: The 2009 shooting at Fort Hood, Texas; the 2012 attack in Benghazi, Libya; and the 2013 Boston Marathon bombing. 

Benghazi attack survivor Kris Paronto said Trump's call for increased vetting was "necessary," adding "terrorists utilize our strengths, compassion and empathy against us. That's what they are doing right now."

On Wednesday, Trump received his first classified intelligence briefing, meeting with national security officials for more than two hours at an FBI field office in New York City. Earlier in the day, Trump suggested he would be skeptical of its contents when he was asked if he trusted the nation's intelligence materials.

"Not so much from the people that have been doing it for our country," Trump told "Fox & Friends". "I mean, look what's happened over the last 10 years...it's been catastrophic."

Also Wednesday, Trump gathered several advisers for a security round table at Trump Tower.

The advisers, including former New York City Mayor Rudy Giuliani, encouraged the GOP nominee to press for more surveillance and more information-sharing with local police departments to fight terror threats if he's elected president. The FBI does share with local police agencies through Joint Terrorism Task Forces.

The Associated Press contributed to this report.