A former Philippine provincial governor accused of masterminding the 2011 murder of an environmental activist and radio show host has surrendered after more than a year in hiding, a government official said Thursday.

In the 13 years since Gerry Ortega was shot dead on the tropical island of Palawan, the region's former governor, Joel Reyes, accused of ordering the hit, has largely remained free due to legal twists and a three-year escape to Thailand.  

State prosecutors allege that 72-year-old Reyes ordered Ortega's shooting, which stands out for its brazenness in a country where hundreds of Filipino journalists and environmental defenders have been murdered.

After a court ordered his arrest last year, Reyes again went into hiding but resurfaced, unbeknownst to authorities, after checking into a Manila hospital, the head of the president's media security task force told AFP. 

Reyes later had his lawyers write to the National Bureau of Investigation "that he really wants to surrender", task force chief Paul Gutierrez said.

"Based on his medical certificate, it appears that he is suffering from many... health complications," he said without providing further details.

Ortega had just finished his morning radio show where he frequently criticized politicians, including Reyes, when he was shot in the back of the head at a second-hand clothes shop in the provincial capital, Puerto Princesa.

Police arrested Ortega's killer and the gun used was traced to a close aide of Reyes, while a bodyguard who hired the assassin later implicated his boss.

Reyes, who has always denied involvement in the murder, was charged in 2012 along with his younger brother.

The siblings soon fled to Thailand, but were deported back to the Philippines in 2015.

The brothers were freed in 2018 after a court voided the case against them, but the charges were reinstated nearly two years later.

In March last year, the Supreme Court told a lower court in Palawan to order the ex-governor's arrest.

The younger brother is out on bail, according to Gutierrez.

"This certainly boosts the government's campaign to create a safe environment for the media," Gutierrez said.

"At the same time, this gives hope to the family of Ortega that the wheels of justice are turning".

Patty Ortega, the journalist's widow, welcomed the defendant's surrender but expects a long courtroom battle ahead.

"I am expecting that the hearing will proceed because I think this is going to be a long process, maybe another 10 years," she told AFP.

"But we will keep on fighting until the end. I'll just keep praying to God. There is only so much you can do."