* Penalty charge for entering no-go zone
* PM Kan harangued by homeless quake survivors
* Engineers struggle to control Fukushima plant (Adds new quake)
By Yoko Kubota and Kazunori Takada
TOKYO, April 21 (Reuters) - Japan said on Thursday it would ban anyone entering a 20-km (12-mile) evacuation zone around the Fukushima Daiichi nuclear plant north of Tokyo, weeks after the tsunami-wrecked facility began leaking radiation.
An earthquake with a magnitude of 6.3 hit eastern Japan on Thursday evening, the U.S. Geological Survey said, but no tsunami warning was issued and there were no immediate reports of any casualties or damage.
Tens of thousands of people left the zone after the March 11 quake smashed the Fukushima Daiichi power station, operated by Tokyo Electric Power (TEPCO), but some have gone back to collect belongings as the utility struggles to contain the world's most serious nuclear crisis since Chernobyl in 1986.
Prime Minister Naoto Kan, already facing criticism for his handling of the crisis, was publicly berated over his government's slow response when he visited one evacuation centre in the devastated region.
Chief Cabinet Secretary Yukio Edano told a news conference that from midnight on Thursday, people could only go into the zone under government supervision.
"We will take strict legal measures against those trying to enter the area ... For residents, all I can say is I ask for their understanding so that no legal action will be taken against them."
Anyone breaking the ban can be fined up to 100,000 yen ($1,200) or be detained by police.
TEPCO has said it may take the rest of the year or longer to bring the plant under control.
More than 130,000 people are living in school gymnasiums and other shelters more than a month after the March 11 quake and tsunami that left some 28,000 dead or missing.
"HOW DO YOU THINK WE FEEL?"
"Are you leaving?" one man shouted as Kan and his entourage headed for the door at a Fukushima evacuation centre. "We are evacuees. Are you just going to ignore us?"
Kan turned back and apologised, only to be berated again.
"You should bring cabinet ministers here and let them try living here themselves. How do you think we feel? We want you to somehow get the nuclear plant under control," one woman said.
Later, Kan told reporters he had been out of touch with the needs of those who had lost their homes.
"I thought I knew how the people here felt but by coming here and actually talking to them, I got the renewed sense that I need to stand in their shoes more and think about their needs," he said.
Kan, already unpopular before the disasters hit, has come under fire from inside his own party as well as the opposition for his handling of the crisis as it drags on.
TEPCO wants a "cold shutdown" of the plant, 240 km (150 miles) from the capital, within six to nine months, a timeline experts say will be tough to meet.
This week it began pumping highly contaminated water from one of the reactors, a key step towards repairing the cooling system that regulates the temperature of radioactive fuel rods.
But water levels were unchanged, the latest in a litany of problems engineers have faced since the crisis began, which has included pumping radioactive water into the sea, to the concern of Japan's neighbours.
The amount of radiation included in water released from April 1-6 into the sea was at 20,000 times the amount Japan's Nuclear and Industrial Safety Agency allows for the plant to release outdoors annually, Kyodo news agency reported.
In a letter published in several Chinese newspapers on Thursday, Kan expressed "extreme regret" about the nuclear disaster, and said Japanese goods were still safe.
TEPCO insists that while fuel rods at three of its six reactors were damaged when they partially melted after the quake, they are not in "meltdown".
The Nuclear and Industrial Safety Agency said the Fukushima Daini nuclear plant, the companion of the crippled Daiichi plant 10 km (6 miles) away, was still leaking radiation but had cleared a key milestone toward stabilising. ($1 = 82.465 yen) (Additional reporting by Chisa Fujioka; Writing by Daniel Magnowski and Linda Sieg; Editing by Robert Birsel)