Washington (CNN) -- Protesters held rallies across the United States and abroad Saturday to mark the one-year anniversary of what many called the "unfair" detention of three American hikers seized by Iranian forces near the Iraqi border.

As part of a weekend of events, vigils were held in a number of locations worldwide Saturday, including Washington, D.C., Minnesota, Arizona, Texas, and Paris, France.

"It's really a global issue," Alex Fattal, older brother of detained American Josh Fattal, told CNN. "We want to send Iran a message."

The three Americans -- Josh Fattal, Sarah Shourd, and Shane Bauer -- were detained after they allegedly strayed across an unmarked border into Iran while hiking in Iraq's Kurdistan region.

At a rally outside the State Capitol in St. Paul, Minnesota, on Saturday, relatives of Bauer -- a Minnesota native -- read a letter from the hiker's mother, according to CNN affiliate KARE.

"Working for Shane's release has become my life," the letter from Cindy Hickey read. "I have closed my doors to my business of 18 years and I do not go anywhere without a phone for fear I would miss that important call, or worst of all missing another brief call from Shane."

Protesters at the St. Paul demonstration carried signs reading "Unfair detainment" and "Bring them home."

"I don't think any of us a year ago today thought we'd still be gathering, still waiting to see Shane, Sarah and Josh come back to us," said rally organizer Laura Breckheimer.

Breckheimer pledged to continue fighting for their release.

"We're not giving up," she said. "We will be here every moment of every day until they release Shane, Sarah and Josh."

In Washington, two friends of the hikers set up a collage of photos and marked a moment of silence at 1:33 p.m. -- the time the Americans were taken into custody.

"It's time to really push the Iranian government, you know, to be compassionate towards a mistake that they [the hikers] may have made, and let them come home," Alexis Stoumbelis told CNN.

The Nation magazine reported last month that two witnesses have said they saw members of Iran's national police force cross into Iraq to apprehend the three.

Tehran has accused the three hikers of being spies, which they deny. Iran's intelligence minister hinted the country may consider releasing them in exchange for the release of Iranian prisoners, according to state media.

The hikers are still being held in Tehran, a year after their July 31, 2009, arrests.

Sen. Amy Klobuchar of Minnesota also spoke out during the St. Paul rally against their detention.

"I have said repeatedly, I do not think that these kids should be a pawn in an international game," she said.

Family members, who say the three were enjoying a recreational hike when they were detained, say they have not been informed of the reasons behind their imprisonment.

"This is unbelievable to us at this point," Shourd's mother, Nora Shourd, told CNN's "American Morning" on Friday. "I mean, it is outrageous that they are still there."

U.S. President Barack Obama called for their release in a statement Friday.

"Their unjust detention has nothing to do with the issues that continue to divide the United States and the international community from the Iranian government," Obama said. "This is a humanitarian imperative, as these three young people are innocent of any crime."

Iran's state-run Press TV refuted reports Saturday that the hikers' detainment is related to an Iranian scientist who accused the United States this month of abducting him.

Shahram Amiri returned to Iran two weeks ago.

A senior Iranian lawmaker told Press TV that the hikers' case is unrelated to Amiri.

The United States has said Amiri was in the country of his own volition.

CNN's Jillian Harding contributed to this report.