BAGHDAD, March 29 (UPI) -- Violence in Iraq Saturday has left at least 75 people dead in Sadr City, the Baghdad neighborhood where Iraqi security forces have targeted Shiite militias.

CNN reported that nearly 500 have been wounded in the days of fighting.

The U.S. military said ground and air operations to back up Iraqi forces killed 23 "criminals" on Friday, CNN reported.

An Iraqi military official said at least 40 members of the Iraqi National Police have abandoned the force recently and taken their U.S.-issued weapons to join radical Shiite cleric Moqtada Sadr's Medhi Army.

Zimbabwe holds presidential election

HARARE, Zimbabwe, March 29 (UPI) -- Voters participating in a national election in Zimbabwe Saturday are deciding whether longtime President Robert Mugabe serves a sixth term in office.

Also vying for the post that Mugabe has held since 1980 are Morgan Tsvangirai of the MDC party and ex-finance minister and independent Simba Makoni, the BBC said.

Election results are expected by Monday. To claim victory, a candidate must have at least 50 percent of the vote to avoid a run-off election in three weeks.

Nearly six million people are eligible to vote in the struggling African nation.

One voter at a polling station in Bulawayo told the BBC that the election was going smoothly.

"There is a long queue behind me but it is moving. People around me are quiet and are waiting patiently to cast their vote," the 23-year-old woman said.

Argentina: Farmer protests end for talks

BUENOS AIRES, March 29 (UPI) -- Protesting farmers in Argentina decided Friday to bring an end to weeks of demonstrations protesting taxes on certain export goods.

Representatives of the farmers said they will halt the demonstrations to hold talks with government officials, La Nacion reported online.

Argentine President Cristina Fernandez Kirchner said this week she would not negotiate with farmers on strike until they call off their protests.

The strike -- which lasted 16 days -- caused food shortages in some parts of the country and severely hampered some exports.

Protesters took to the streets of the capital, Buenos Aires, leading to clashes with authorities.

Puerto Rico governor pleads not guilty

SAN JUAN, Puerto Rico, March 29 (UPI) -- Puerto Rican Gov. Anibal Acevedo Vila pleaded not guilty Friday to corruption charges linked to alleged illegal campaign fundraising.

Acevedo was welcomed by a throng of flag-waving supporters when he arrived at the courthouse Friday to enter his plea, El Nuevo Dia reported online.

The Puerto Rican leader was charged this week with conspiracy, making false statements, wire fraud, federal program fraud and tax crimes related to campaign financing of his 1999-2000 and 2001-2002 campaign for resident commissioner of the commonwealth of Puerto Rico, and his subsequent 2004 gubernatorial campaign.

Acevedo and co-defendant Luisa Inclan Bird, his legal adviser, allegedly solicited and accepted illegal campaign donations from Acevedo's family and staff.

"Our democratic system cannot function when public officials act as though they are above the law. Public officials must comply with the law and those who do not comply will be held accountable," Luis Fraticelli, special agent in charge of the FBI's San Juan Field Office, said in a news release.

U.S. cities to dim lights for 'Earth Hour'

CHICAGO, March 29 (UPI) -- Some of Chicago's lights will dim for an hour Saturday night as part of a campaign to draw attention to global climate change, organizers said.

More than 500 local businesses have agreed to be a part of the Windy City's first Earth Hour, said Sadhu Johnston, Chicago's chief environmental officer.

Among the landmarks taking part in the event are Wrigley Field's marquee, Michigan Avenue storefronts and the Sears Tower's antennae.

Other cities participating in Earth Hour are Atlanta, Phoenix and San Francisco, the newspaper said.

"I don't expect the actual hour is going to save enough power to make a huge difference" in affecting the global climate, Johnston said, adding that the event is aimed at getting people to talk about global warming.

"There are lots of things people can do in their own lives to help us be a green city," he said. "That may mean turning off lights when they are not using them, or unplugging cell phone chargers when they are not doing anything."