Federal immigration enforcement agents last weekend arrested 121 migrants for deportation, Homeland Security Secretary Jeh Johnson said on Monday, starting a wave of removals of parents and children, mainly from Central America, who came during the border surge in 2014 and failed to win asylum in immigration courts.

Most of the arrests were in Georgia, Texas and North Carolina, officials said, and were of migrants who had lost their cases and were ordered deported by immigration judges. The deportations are part of “concerted nationwide enforcement operations” to achieve a “greater rate” of deportation of parents who crossed the border illegally with their children, Mr. Johnson said.

Obama administration officials are scrambling to stem a new influx of people crossing the South Texas border since July, many of whom are families or children without their parents, often fleeing rampant gang violence in El Salvador, Honduras and Guatemala. The administration wants to send a stronger message to the region that many migrants crossing illegally, even mothers and children, will be sent home.

“Our borders are not open to illegal migration,” Mr. Johnson said.

The deportations have provoked outrage from immigrant and Latino groups, just when they had been organizing support for President Obama because of his efforts to provide protections for immigrants already living in the country illegally, which have been held up by federal courts.