A Chinese Foreign Ministry spokesman pushed back on Wednesday against assertions by Lt. Gen. Michael T. Flynn, who is President-elect Donald J. Trump’s choice for national security adviser, that China was allied with “radical Islamists.”

The spokesman, Lu Kang, was asked at a regularly scheduled news conference in Beijing about Mr. Flynn’s accusations, which were made in a book released in July that he wrote with a co-author, “The Field of Fight: How We Can Win the Global War Against Radical Islam and Its Allies.”

“I hope everyone who takes a responsible attitude and is devoted to safeguarding China-U.S. relations and boosting China-U.S. cooperation can base their opinions on facts when taking a position,” Mr. Lu said. “Only in this way can mutual trust be enhanced.”

Mr. Flynn has said the United States must lead a global campaign against “radical Islam.” He has on occasion pushed conspiracy theories. For example, after the attack on the American diplomatic compound in Benghazi, Libya, in 2012, he kept asking intelligence officers working under him at the Defense Intelligence Agency in the Pentagon to look for involvement by Iran in the assault. There was no evidence of any ties to Iran.

In his book, Mr. Flynn mentions China and North Korea a half-dozen times.

In one passage, he wrote, “The war is on. We face a working coalition that extends from North Korea and China to Russia, Iran, Syria, Cuba, Bolivia, Venezuela and Nicaragua. We are under attack, not only from nation-states directly, but also from Al Qaeda, Hezbollah, ISIS and countless other terrorist groups.”

In another, he said, “No surprise that we are facing an alliance between radical Islamists and regimes in Havana, Pyongyang, Moscow and Beijing. Both believe that history, and/or Allah, blesses their efforts, and so both want to ensure that this glorious story is carefully told.”

Mr. Flynn did not respond to a request for comment on Wednesday.

China is a secular Communist nation that has expressed concern about the spread of Islamic extremist ideas within its borders. It has said religious extremists are responsible for violence in Muslim areas of the western region of Xinjiang, and it has asked the United States for cooperation in counterterrorism operations there. American officials say they are reluctant to enter into close cooperation on Xinjiang matters, as some ethnic Uighurs and human rights groups say Chinese officials are violating human rights in Xinjiang.

On Tuesday, Mr. Trump fired Mr. Flynn’s son, Michael G. Flynn, from his transition team after the younger Mr. Flynn used Twitter to support a conspiracy theory involving a pizza parlor in Washington, which was the subject of fake news stories. This week, a man citing that theory was arrested after firing a rifle in the restaurant, the police said.