Officials of a rural Maryland town illegally discriminated against a Muslim group by barring them from building a mosque and holding annual conventions on land zoned for farming, the property's owner claimed in a federal lawsuit filed Monday.

The complaint was filed not by the Ahmadiyya Muslim Community USA but by developer David Moxley and his father Robert, who had planned to sell the group 224 acres in Walkersville for about $6 million.

The Silver Spring-based religious group canceled the land purchase earlier this year after the town's three-member Board of Zoning Appeals voted unanimously to reject their request for a special exception to land-use restrictions.

Officials of the town of 5,600 based their denial largely on open space preservation concerns and fears that the thousands of people attending the group's annual, three-day Jalsa Salana national convention would overwhelm the community's roads and emergency services.

Moxley said the convention each June draws an average of 4,500 people. This year's gathering, held in Harrisburg, Pa., drew nearly 10,000 to see the group's spiritual leader making a rare U.S. visit, event coordinator Harris Zafar said.

David and Robert Moxley's complaint, filed in U.S. District Court in Baltimore, alleges that town leaders conspired to block the Ahmadis by adopting new land-use restrictions, including one barring places of worship on agricultural land, after the group publicly announced its plans for the site.

"I've never seen a worse example of hostility toward a religious group accomplished through the zoning process as by the town of Walkersville," said the Moxleys' lawyer, Roman P. Storzer, a Washington attorney specializing in religious land-use discrimination cases.

Walkersville town attorney Danny O'Connor didn't immediately return a call from The Associated Press seeking comment on the lawsuit.

The complaint alleges violations of the U.S. Constitution's First Amendment, which guarantees free exercise of religion, and the 14th Amendment, which provides equal protection to all.

It alleges violations of the federal Religious Land Use and Institutionalized Persons Act, enacted in 2000 to bar land-use regulations that would discriminate against a religious organization.

The plaintiffs also alleged violations of the federal Fair Housing Act, because the imam of the region's 20-family Ahmadiyya congregation had planned to live on the property, and of the Maryland Constitution's Declaration of Rights.

Storzer said the lawsuit seeks a court order forcing the town to permit the uses sought by the Ahmadis, a declaration that the town violated civil-rights protections and payment of unspecified damages to the Moxleys.

The Ahmadis are not joining the lawsuit. The group announced on June 8, three days after the board's final decision, that they would "leave the matter in the hands of God" and that participating in litigation "would be tantamount to trespass on his hallowed ground."

However, Ahmadiyya community spokesman Syed Ahmad did not rule out the possibility of buying the site if the Moxleys triumph.

"I don't know the answer," he said in an interview with The Associated Press before the lawsuit was filed. "I think we have moved away in our mind from Walkersville."

The Ahmadiyya, or Ahamdis, believe that their spiritual leader, Hadhrat Mirza Ghulam Ahmad, who died in 1908, was a prophet of God. They regard themselves as Muslims but they have been barred from practicing their faith in Pakistan, resulting in violent clashes with hard-line Muslims.