PORT-AU-PRINCE, HAITI, OCT. 13 -- Police shot and killed presidential candidate Yves Volel today as he delivered a speech in front of police headquarters to demand the release of a prisoner, witnesses said.

Plainclothesmen beat and shot several times at Volel, who was struck once in the head and died instantly, Radio Metropole reported. A reporter for TeleHaiti corroborated the account.

Police cleared the area of bystanders and reporters and photographers' cameras were confiscated. The body was taken to the State University Hospital morgue.

In a communique from police headquarters, police did not address allegations that they killed Volel. They said he had been armed and that they were looking for "his accomplices."

Businesses in the area near the National Palace shut and barred their doors in apparent anticipation of further violence.

Volel, an attorney, was a minor candidate for president but a persistent critic of the governing junta of Lt. Gen. Henri Namphy. Volel's center-left Christian Democratic Rally, formed last year, is an offshoot of the larger Christian Democrat Party of Sylvio Claude.

Volel invited reporters to accompany him to the police station, where he demanded the release of Jean Raymond Louis, who allegedly has been held without trial for the past month.

"They arrested Louis without a warrent for political reasons," Volel told Radio Metropole in an interview broadcast yesterday. "The constitution forbids that and says everybody has a right to a lawyer, so I will go at 10 a.m. {Tuesday} to offer him my services."

Volel supported the antigovernment strikes and demonstrations of June and July that shut down Haiti's major cities. He carried a Colt .45-caliber revolver. In July, Volel said he was attacked by armed men who sprayed his jeep with machine-gun fire. He claimed he returned fire.

Volel is the second presidential candidate to be killed this year. Louis Eugene Athis was hacked to death in August on the steps of a church by peasants who accused him of being a communist.

Volel, 54, was one of about 30 candidates who have registered to run for president in the national elections set for Nov. 29.