Sri Lanka's government voted on Friday to increase the mandatory retirement age of all judges by two years as part of reforms opposed in parliament and by the influential bar association.

President Anura Kumara Dissanayake unveiled two bills last month as part of wider judicial reforms he said are needed to reduce legal delays in hundreds of thousands of cases.

The bills also seek to increase the number of courthouses, create new appellate courts outside the capital and recruit additional magistrates and staff to speed up trials, as well as the recruitment of 10,000 police officers.

Opposition legislators wore black in protest against the two bills before Friday's vote.

Raising the retirement age of judges required a two-thirds majority in parliament in order to amend the constitution, and 158 MPs in the 225-seat assembly voted in favour.

The two-year extension will now apply to 411 judges in Sri Lanka.

Opposition Leader Sajith Premadasa accused the government of turning the judiciary into a pawn of the executive.

"Attempting to control our country's noble, free and independent judiciary through a constitutional conspiracy is a shameless and despicable act," Premadasa told parliament.

Premadasa led thousands of supporters in a protest outside parliament at the start of two days of debate on Thursday.

Dissanayake has argued that the reforms are necessary to clear a backlog of 1.1 million cases. Criminal proceedings usually take more than 17 years in Sri Lanka, while civil cases can take generations to conclude.

The influential Bar Association of Sri Lanka also opposed the bills and called for a national referendum.

However, the Supreme Court ruled that a two-thirds majority in parliament was sufficient and that a referendum was not needed.

The association also said the legislation would effectively extend the tenure of Chief Justice Preethi Padman Surasena, who was due to retire in December after being elevated last year.

Several opposition parties have accused Surasena of being biased in favour of the government. Dissanayake's administration denies the claim.

The judicial overhaul comes as authorities intensify corruption investigations involving former president Mahinda Rajapaksa and members of his family. They deny any wrongdoing.