GEOFF BENNETT: Nearly half-a-century after its birth from a bloody Civil War, Bangladesh has made significant strides in reducing poverty.

One of the best known architects of this progress is Muhammad Yunus, who popularized the concept of microfinance.

But Yunus has run afoul of his country's prime minister and has faced a series of legal challenges and now criminal charges.

Fred de Sam Lazaro has our report, part of his series Agents for Change.

FRED DE SAM LAZARO: He's won the Presidential Medal of Freedom and the Congressional Medal of Honor.

SEN. RICHARD DURBIN (D-IL): Make no mistake, Muhammad Yunus is a genius.

FRED DE SAM LAZARO: Nearly a half-century ago, this Vanderbilt-trained economist left a teaching career in Tennessee, saying he was called to serve his newly independent war-shattered nation.

MUHAMMAD YUNUS, Founder, Grameen Bank: People were dying of hunger.

And I find myself in a very strange situation teaching elegant theories of economics.

Those elegant theories have no use for people who are dying.

FRED DE SAM LAZARO: He did test one economic theory, offering a few women loans to start small enterprises like a poultry farm.

It worked, he told me in this 2001 interview.

MUHAMMAD YUNUS: People are paying back, and they paid back every penny without any hitch, so I got very excited.

So I thought I should have my own bank.

FRED DE SAM LAZARO: The Grameen Bank grew quickly, 97 percent owned by millions of its female borrowers, success that earned him the Nobel Peace Prize in 2006.

Today, Grameen has a large footprint in Bangladeshi society, far beyond microlending with affiliated companies that sell cell phone service and food products.

There's even a nursing school.

Its global reach includes Grameen America, which last year loaned $1 billion to low-income Americans.

All profits are plowed back into expanding the mission.

Yunus has won friends in the highest places across the globe, except at home.

In January, Yunus, who is 83, and three senior Grameen colleagues were sentenced to six months in prison for violating labor laws, charges he calls politically motivated.

He was released on bail, but this case is only the beginning of his legal troubles.

He faces more than 100 other charges of labor law violations and graft.

What's life like as you go into work these days?

MUHAMMAD YUNUS: Well, not very comfortable.

FRED DE SAM LAZARO: I reached Yunus in his Dhaka office, where, days earlier, a group of about 35 men appeared unannounced to take over and began padlocking the place at the end of each day.

MUHAMMAD YUNUS: They said: "We are the new management of this coming bank that is under government control these days."

We went to the police.

Police would not help us.

FRED DE SAM LAZARO: This latest disruption is a dramatic escalation of actions targeting Yunus that began in 2011, when he was removed as chair of the Grameen Bank.

MUHAMMAD YUNUS: Because government rule doesn't permit anybody to remain in government job after 60.

I said, this is not a government bank.

This is a bank owned by the poor women.

Anyway, I was forced out.

FRED DE SAM LAZARO: Can you help explain what is at the root of this antagonism?

MUHAMMAD YUNUS: It beats me.

FRED DE SAM LAZARO: What's not in doubt is that his chief antagonist is the country's prime minister.

MUHAMMAD YUNUS: She calls me as a bloodsucker of the poor people.

FRED DE SAM LAZARO: Sheikh Hasina recently won a fourth term in elections, widely discredited and boycotted by opposition parties.

Most of their leaders are in prison.

She's publicly denounced Yunus as a corrupt opportunist in a spat that experts trace back to 2007 and a time of political upheaval, when Yunus toyed with forming his own party.

It was at the urging of the country's military leaders, he says, and short-lived.

MUHAMMAD YUNUS: About 10 weeks, that's about it.

And after the end of these 10 weeks, I declared that, no, I'm not going to create any party because I cannot handle politics.

That's my -- not my cup of tea.

FRED DE SAM LAZARO: But experts say Prime Minister Hasina might still perceive Yunus, a revered civic figure, as a political threat.

Despite pleas for more than 200 global luminaries, from former President Obama to U2's Bono, to end the -- quote -- "legal harassment," the campaign against Yunus has only intensified.

ALI RIAZ, Illinois State University: This case is an example of a weaponization of judiciary.

FRED DE SAM LAZARO: Political scientist Ali Riaz at Illinois State University says Sheikh Hasina has tightened her grip on power.

Geopolitical realities allow her to resist Western pressure, he says, and the Yunus case sends a chilling message domestically.

ALI RIAZ: The prime minister has received unqualified support from two powers, that is Russia and China, not to mention India.

India has been the principal backer of this government since 2009.

And this is the message to the Bangladeshis that if Professor Yunus can be persecuted and punitive measures can be taken, you are nobody.

We can take -- do anything.

FRED DE SAM LAZARO: So, what might Professor Yunus be facing in the weeks and months ahead?

ALI RIAZ: I'm afraid he might actually end up in jail.

I'm sorry to say it.

It breaks my heart to say, but it could happen.

FRED DE SAM LAZARO: Government officials insist the judicial process is independent of political interference.

We contacted the Bangladesh embassy in Washington for comment, but did not receive a response.

MUHAMMAD YUNUS: I, as the chairman of these companies, never received any salary, any kind of fee for my attending meetings, nothing.

FRED DE SAM LAZARO: For his part, Yunus continues to assert his innocence.

He says he's received several offers of asylum abroad, but has ruled out exile.

MUHAMMAD YUNUS: This is where I work with my -- with people who have worked together for years and years.

We don't -- I don't want to abandon them and go someplace else.

I cannot do that.

FRED DE SAM LAZARO: He has a bail hearing on March 3, also the date when an anti-corruption commission is scheduled to release what many colleagues fear will be incriminating results from a yearslong investigation of Yunus' activities.

For the "PBS NewsHour," I'm Fred de Sam Lazaro.

And Fred's reporting is a partnership with the Under-Told Stories Project at the University of St. Thomas in Minnesota.