A magnitude-7.1 aftershock has rattled Japan on the one-month anniversary of a massive earthquake that spawned a deadly tsunami.

A warning has been issued for a 3-foot (1-meter) tsunami, the same as after another 7.1 aftershock that shook the northeast coast last week. There was no tsunami after that quake.

People at a large electronics store in central Sendai screamed and ran outside, though the shaking made it hard to move around. Mothers grabbed their children, and windows shook. After a minute or two, people returned to the store.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

FUKUSHIMA, Japan (AP) _ Sirens wailed and people bowed their heads and wept along Japan's devastated northeast coast Monday as they marked a month since the tsunami that killed up to 25,000 people and unleashed a persistent nuclear crisis.

The tsunami-flooded Fukushima Dai-ichi nuclear plant is still leaking radiation after its cooling systems were knocked out by the tsunami, and the government Monday urged even more people living around the complex to leave within a month, citing concerns about long-term health risks from radiation as the crisis wears on.

People living within 12 miles (20 kilometers) already have been ordered to leave because of concerns about radiation in the air. Other people farther out had been advised to stay indoors.

Chief Cabinet Secretary Yukio Edano said Monday that residents of five more communities, some more than 20 miles (30 kilometers) from the plant, are being urged to leave because of high levels of radiation.

"This is not an emergency measure that people have to evacuate immediately," Edano said. "We have decided this measure based on long-term health risks."

It was one more reminder of how long it could take to resolve the nuclear crisis. With that still ongoing, thousands of bodies yet to be found and more than 150,000 people living in shelters, there was little time Monday for reflection on Japan's worst disaster since World War II.

"My chest has been ripped open by the suffering and pain that this disaster has caused the people of our prefecture," said Yuhei Sato, the governor of Fukushima, which saw its coastal areas devastated by the tsunami and contains the damaged plant at the center of the nuclear crisis. "I have no words to express my sorrow."

People in hard-hit towns gathered for ceremonies at 2:46 p.m., the exact moment of the magnitude-9.0 quake that spawned the tsunami March 11.

In a devastated coastal neighborhood in the city of Natori, three dozen firemen and soldiers removed their hats and helmets and joined hands atop a small hill that has become a memorial for the dead. Earlier, four monks in pointed hats rang a prayer bell there as they chanted for those killed.

The noisy clatter of construction equipment ceased briefly as crane operators stood outside their vehicles and bowed their heads.