The leftist president was forced to deliver his remarks via a video call on his phone from a car in Tuxtla Gutierrez, the capital of Chiapas, while inaudible protesters shouting and speaking on a megaphone could be heard in the background.
Mexican teachers often strike, and Lopez Obrador has previously praised powerful teaching unions that have in the past protested, sometimes violently, against centrist and right-wing Mexican governments.
The latest protests were related to the most recent teaching reforms, Mexican newspapers said.
Since assuming office in December 2018, Lopez Obrador has used his morning news conferences - which begin at 7 a.m. and can last over two hours - to set the political agenda and take critics to task.
By midmorning, la mañanera, as the morning news conference is colloquially known, was trending on Twitter in Mexico.
"I've never seen anything like this," one user wrote. "Mexico had enough."
But not everyone agreed. "My right to information during la mañanera was not respected today in Chiapas," another user posted.
Most of the morning news conferences take place in Mexico City, but he sometimes conducts them while traveling around the country.
"They have a right to protest. We will respect that," Lopez Obrador said, in reference to the teachers, his video message transmitted on a screen in the background of an empty lectern and the Mexican flag. "We are offering them dialogue."
"I will stay here as long as necessary."
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