The Philippines' justice secretary on Sunday backed calls to allow judges and lawyers to carry firearms amid a rising incidence of attacks targeting them.

Justice Secretary Leila de Lima said judges and lawyers were also being encouraged to improve practical shooting and driving skills as a precaution against possible ambush attacks.

"Their line of work make them natural targets of harassment and violence, especially because of weak enforcement of laws and a prevailing culture of impunity," de Lima told AFP.

De Lima however said she favoured only a "selective, on a case-by-case" basis to allow judges and lawyers to carry firearms.

"And only on a reasonable showing of security threats, and purely for self-defence purposes only," de Lima said.

The National Union of People's Lawyers, an association of human rights defenders, said at least 15 lawyers and judges were killed last year in attacks police believe were linked to their work.

Two lawyers were among 57 people killed in the country's worst political massacre that took place in the strife-torn southern province of Maguindanao, the group's spokesman Julius Garcia Matibag said.

Matibag welcomed de Lima's suggestion, but said greater importance should be given to arresting, prosecuting and jailing suspects.

"That is a good way for lawyers for judges and lawyers to defend themselves if there are threats against their life," Matibag said.

"But the best way for the courts to address this matter is to see to it that there will be a conviction, so that bad elements out there will not be encouraged to simply kill a lawyer or a judge," he said.

Rights groups have said a culture of impunity pervades the Philippines, where there are more than 1.1 million unlicensed firearms, on top of the 1.3 million guns in the hands of authorised police and military personnel.

The combined tally means there is roughly one firearm for every 40 Filipinos.