"One awful event after another. Leader McConnell must call the Senate back for an emergency session to put the House-passed universal background checks legislation on the Senate floor for debate and a vote immediately", Senator Chuck Schumer said.
Speaker Nancy Pelosi echoed Schumer's statement and also called for urgent action.
"We cannot allow another family or another community to suffer the pain and anguish of gun violence. We have a responsibility to the people we serve to act. The Republican Senate must stop their outrageous obstruction and join the House to put an end to the horror and bloodshed that gun violence inflicts every day in America. Enough is enough", she said in a statement released on her website.
At least 20 people were killed and 26 more injured after a gunman opened fire in a Walmart Cielo Vista Mall in El Paso, Texas, in the city of El Paso, Texas, on Saturday evening.
Hours later, another gunman attacked people in the city of Dayton, Ohio, killing nine and injuring at least 26 people. The shooter's sister was among those killed in the massacre.
US President Donald Trump ordered to lower the flags to half-staff to pay tribute to the victims of the deadly shootings.