A Cambodian political analyst who was a well-known government critic was shot dead Sunday morning in what police say was a personal dispute over money.

Kem Ley, 45, was killed at a gas station mini-mart complex in Phnom Penh and his attacker arrested shortly after, said national police spokesman Gen. Kirth Chantharith. He said the suspect claimed to have shot Kem Ley because he failed to pay him back for a loan.

The killing comes at a time of political tension that began last year with legal and other pressures on the opposition Cambodia National Rescue Party by the government of Prime Minister Hun Sen.

The party issued a statement mourning his loss as someone who worked to promote his country's economy and democratic system. It condemned the killing and called on authorities to conduct a serious investigation to give justice to his family.

Kem Ley was often critical of the government, and was widely known because he was frequently heard on the popular Cambodian-language services of Radio Free Asia and Voice of America, U.S. government-funded services that are among the few independent news sources. He was also frequently quoted in the country's handful of independent newspapers.

One of his most recent commentaries was about a report issued last week by the London-based research and advocacy group Global Witness that alleged that Hun Sen and his family enriched themselves and keep power through corruption.

Kem Ley is the most prominent government critic to be killed since trade union leader Chea Vichea in 2004. In 2012, conservation activist Chut Wutty was gunned down by a soldier.

Violence has long played a prominent role in Cambodian politics, though it often is carried out in the countryside where it gets little attention. Activists and members of the political opposition are frequent targets, and attackers are rarely brought to justice.

In 1997, a grenade attack on a rally held by opposition leader Sam Rainsy killed at least 16 people and wounded more than 100, with no one brought to trial. Last year, two opposition lawmakers were dragged from their cars and badly beaten by members of a pro-government mob. In both cases, critics charged that members of Hun Sen's personal bodyguard unit were involved in the attacks.

Rainsy is currently in exile to avoid what he asserts is a politically motivated prosecution, and his deputy, Kem Sokha, has been living for weeks at party headquarters trying to avoid what he also says is a specious case against him.