In a glimpse of the post-apocalyptic, office towers languished without workers. Sidewalks lay abandoned. Parking spaces were plentiful. Emptiness enveloped downtown and Government Center, it haunted the Back Bay and Kendall Square.

“It’s a ghost town,” cab driver Jimmy Carbone said. “It’s kind of scary.”

An unprecedented manhunt held metropolitan Boston hostage as police searched house by house for a suspect in the Marathon bombings, leaving almost 1 million people under siege.

The region felt as if gripped by martial law: Police armed with rifles patrolled empty roads. Soldiers outnumbered shoppers in Downtown Crossing. Marksmen in camouflage fatigues crawled across the roof of a shed in a backyard in Watertown.

“Keep the doors locked,” Governor Deval Patrick warned at an afternoon press conference. “It is important that folks remain indoors.”

Authorities shut down all Massachusetts Bay Transportation Authority service, citing safety concerns as they halted subways, trains, and buses. City and town halls remained closed, as mayors and selectmen tracked the crisis behind locked doors. Public works departments canceled trash pickups, keeping garbage trucks off streets. Courthouses kept their doors shut. Taxis were pulled off roads.

The crisis kept the Red Sox off the diamond at Fenway Park and the Bruins off the ice at TD Garden. It shuttered renowned colleges and universities. Armed guards checked identification at world-famous hospitals, where elective surgeries were canceled and access was restricted to staff and people in need of urgent medical care.

From Dudley Square to the Seaport, Cambridge to Kenmore Square, businesses were shuttered.

People stayed home. And a disconcerting silence filled the air, interrupted by the distant wail of sirens and the thwack, thwack of helicopters.

The quiet overwhelmed Kendall Square in Cambridge, where mayhem reignited Thursday night when an MIT police officer was shot and killed, apparently in a confrontation with the two suspects in the Boston Marathon bombing.

Most mornings, Kendall Square pulses with the energy of scientists, entrepreneurs, and tech workers rushing to Microsoft and Biogen Idec. But at 9 a.m. Friday, entire office blocks remained uninhabited, and the Massachusetts Institute of Technology was closed. Au Bon Pain appeared to be the only restaurant open.

“It’s not even like this on a Sunday,” said Sujan Rijal, an Au Bon Pain employee.

Along Massachusetts Avenue in Boston, armed law enforcement officers in neon vests guarded almost every intersection from the Back Bay to Roxbury. The stillness hung over Kenmore Square, where normally clogged streets were clear and parking lots were virtually empty. Tourists walked aimlessly, unable to board trains or buses.

“What is this world coming to?” asked Guy Dixon, a maintenance and security worker at a rooming house for women on Charlesgate West. “This is too close to home.”

The lock-down paralyzed Boston, Cambridge, Waltham, Newton, Belmont, and Brookline as residents hunkered inside, under authorities’ order.

But it turned Watertown into an occupied territory as armored vehicles and police, clad in riot gear and hoisting machine guns, hunted for a terrorist on suburban streets.

In other towns and residential neighborhoods of Boston, streets remained almost frozen, like a snow day with no snow. It was school vacation week, so children were trapped at home indoors with spring temperatures topping 70 degrees.

“It was a day to keep kids away from the TV,” said Kerry O’Brien of West Roxbury, who played the board game Clue with her 15-year-old daughter, Maggie Skaza, when the teen wasn’t memorizing a passage from “Catcher in the Rye” for her upcoming declamation at Boston Latin. “We’re not going to let those guys ruin our life. We had some fun.”

In Brookline, it was, “quiet, very quiet,” said Betsy DeWitt, chairwoman of the Board of Selectmen. “People who have been asked to stay in are staying in.”

That held true in Jamaica Plain, too, where City Councilor Matt O’Malley sat in his living room obsessively tracking the manhunt on television and the Internet.

“It’s been almost eerily quiet the last couple of hours,” O’Malley said. “I live on the Jamaicaway, which is usually crawling with traffic.”