President Rodrigo Duterte has warned Philippine police and military to shoot dead anyone "who creates trouble" during a month-long lockdown of the island of Luzon — the largest and most populous island in the Philippines — enforced to halt the spread of the coronavirus.

Key points: Police arrested 21 residents of a slum in Manila for staging an "unauthorised protest"

Police arrested 21 residents of a slum in Manila for staging an "unauthorised protest" They will face criminal charges of violating a new law that requires millions of people to stay home under quarantine

They will face criminal charges of violating a new law that requires millions of people to stay home under quarantine Cases of COVID-19 have reached 2,311 in the Philippines with 96 deaths

"My orders are to the police and military … that if there is trouble or the situation arises that people fight and your lives are on the line, shoot them dead," he said in a late-night televised national address.

"Instead of causing trouble, I'll send you to the grave."

Mr Duterte's warning came after police arrested 21 residents of a slum in Manila's Quezon City for staging an "unauthorised protest" demanding government food aid.

The residents of the shantytown claimed they had not received any food packs and other relief supplies since the lockdown began more than two weeks ago.

Those arrested included six women.

Police Brigadier General Ronnie Montejo said they will face criminal charges of violating a new law that requires millions of people to stay home under quarantine.

The residents ignored an appeal by the police to return home.

"Let this be a warning to all. Follow the Government at this time because it is critical that we have order," Mr Duterte said.

"Do not go around causing trouble and riots because I will order you detained until this COVID-19 [outbreak ends]."

Amnesty International Philippine called on Mr Duterte to immediately end any incitement to violence and urged concerned agencies to investigate police members using disproportionate force.

"It is deeply alarming that President Duterte has extended a policy of shoot to kill, a devastating hallmark of his presidency, to law enforcement agencies in the community quarantine," Amnesty International Philippine section director Butch Olano said.

"Deadly, unchecked force should never be referred to as a method to respond to an emergency such as the COVID-19 pandemic."

'Mass tests not mass arrests'

The Philippines recorded 227 new coronavirus cases and eight more deaths on Wednesday. ( AP: Aaron Favila )

Kadamay, a group representing Manilla's urban poor, said desperate residents gathered spontaneously to ask for food and medical aid.

The group denied it was a left-wing move to undermine Mr Duterte's administration.

Other residents later held a rally to demand the release of those arrested, holding posters that read, "mass tests not mass arrests".

The Philippines recorded 227 new coronavirus cases and eight more deaths on Wednesday, the health ministry said.

The latest figures brought the total number of infections and deaths in the country to 2,311 and 96, respectively.

Health ministry official Maria Rosario Vergeire said they have opened new labs and run more than 15,000 tests, a five-fold jump from about 3,000 last week, adding that more hospitals were seeking government approval to function as testing centres.

"We have six more laboratories to conduct tests," Ms Vergeire said.

"We are also conducting contact tracing to find possibly infected persons."

The Philippines, the third country after China and Italy to order home quarantine for a large part of its population of 107 million, had until recently reported fewer cases than expected, with many deaths.

Authorities had attributed that to a lack of testing kits and lab capacity.

Mr Duterte has put retired generals among his cabinet in charge of the task force battling the crisis, saying its management requires military-style discipline.

ABC/wires