The temporary restrictions would be in place “for an initial period of 30 days,” and could be prolonged, European Commission President Ursula von der Leyen announced on Monday.
Family members of European nationals, essential staff, such as doctors and nurses, and people transporting goods to the EU will be exempted from the upcoming measures.
“The less travel, the more we can contain the virus,” von der Leyen said during a press conference, which followed a video conference between G7 leaders.
She appeared confident that the European Council will sign off on the restriction in a Tuesday vote.
The country's land borders were closed Monday, Interior Minister Fernando Grande-Marlaska announced. The closure does not include Spanish nationals and residents, workers required to cross the border, and the transport of goods.
Some 47 million Spanish residents have been banned from leaving their homes — with the exception of those going to work, buying food, going to a hospital, or supporting an elderly person or child in their care.
The few people still walking in Madrid's eerily empty parks on Monday were met by buzzing drones overhead, instructing them to: “Go home!”
Priests in the deeply Catholic country are celebrating Mass alone, with services shown only on TV or via social media. Restaurants and bars have been closed. And cultural sites like the Prado Museum and Royal Palace in Madrid are also shut, as part of the tough measures announced by Spanish Prime Minister Pedro Sanchez on Saturday.
The same day, the government announced that the prime minister's wife, Maria Begona Gomez Fernandez, had tested positive for the virus. The couple are both “well” and following preventative measures at their official residence, La Moncloa Palace in Madrid, the statement added.
Spain's 15-day state of emergency comes after school closures were announced last week.
Tougher measures are expected to follow after the health ministry identified a 25% daily increase in the number of cases, its emergencies coordinator, Fernando Simon, said Monday.
Metro falls silent but commuter trains packed
Around half of the cases reported in the country so far have been in Madrid, where the region's president, Isabel Diaz Ayuso, has also tested positive for the virus, officials said.
It was a different story on the trains however, which passengers from out of town rely on to get into the city. At the central Atocha train station, commuters lined the platform and many told CNN that safe distances were not being maintained on board.
“It's shameful,” passenger Librada Aguilera told CNN. “There are fewer trains which means they are very full. I had to travel with people all around me, very close.”
“What is the point of me being at home all weekend if I am going to have to travel like this today?” she asked, adding that a “safe distance” was not being implemented.
“I can't work from home, so I don't have another option but to travel like this,” she said.
Elsewhere in the city, some supermarkets were going to extremes to stop customers standing too close to one another, by taping markings on the ground.
Supermarkets were largely empty on Monday, with cashiers changing their gloves and disinfecting conveyor belts after every every customer, CNN reporters found.
“Most Spaniards are compliant” with the restrictions, one police officer patrolling the streets of Madrid told CNN. “Though they are taking far too much time to walk the dog or shop for food,” he said, adding that this was “a trick” to stay outside for longer.
To get people off the streets, police can issue fines starting at $100. But the officer admitted that “fines won't solve this.”
“We all have to do this in solidarity, knowing that everyone is staying at home,” he said.
Some hotels have offered up their beds to help ease the strain on hospitals. On Monday, the country's Parachute Brigade delivered 45 hotel beds in army trucks to Alcalá de Henares in Madrid.
Elsewhere, high-profile budget airlines Ryanair and Easyjet announced on Sunday they would be canceling and reducing flights to and from Spain.
CNN's Scott McLean, Sarah Dean and Mia Alberti contributed to this report.