The United States has withdrawn all assistance to St. Lucia's police force over concerns about allegations of unlawful killings, the leader of the small Caribbean country announced.

St. Lucia Prime Minister Kenny Anthony said the matter focuses on 12 people fatally shot by police in 2010 and 2011 while another administration was in power. Relatives of the victims and other critics insist the men were murdered and police had a "hit list" of people deemed to be criminals.

The killings occurred during a security initiative called "Operation Restore Confidence" as the tourism-dependent island grappled with a worrying rise in violent crime. Five of the men were killed in a single police operation in the southern town of Vieux Fort.

Washington already had blocked St. Lucia officers from participating in U.S.-financed training programs and recently prevented the top commissioner from attending a law enforcement conference, Anthony said.

On Wednesday, a State Department official, who spoke on condition of anonymity, said St. Lucia was informed about the decision Aug. 16.

In an address to the country of some 162,000 people late Tuesday, Anthony said the action was based on a U.S. law that requires the State Department to stop assistance to a foreign security force if there is credible information that a gross violation of human rights has occurred.

In its recent annual report on the island, the State Department complained of the slow pace of investigations into the deadly police shootings.

In St. Lucia and other former British colonies, coroners investigate unexplained deaths by holding an inquest. Anthony said six inquests had been held into the 12 killings so far and coroners returned a judgment of "death by lawful act." The inquest into the five men killed in Vieux Fort continues.

"Since the United States has decided to impose sanctions on members of the Royal St. Lucia Police Force, then it is reasonably clear that it does not have confidence in the outcomes of the inquests," Anthony said.

He said his administration will work closely with the U.S. to resolve the issue, emphasizing that the island "values its close cooperation with the United States in security matters."