YANGON (AFP) -- Myanmar's de facto leader Aung San Suu Kyi has broken a month long silence on the daylight assassination of her advisor, calling his killing a "great loss" for the country's democracy struggle.

Ko Ni, a prominent Muslim lawyer and critic of Myanmar's powerful military, was shot dead on 29 January outside Yangon airport in a murder that sent shockwaves through the country's young civilian government.

A taxi driver, Ne Win, was also killed trying to stop the gunman who was arrested. Authorities say he was hired by a former military officer now on the run.

Suu Kyi's ruling National League for Democracy party branded the killing a political assassination and "terrorist act" against their policies.

But Suu Kyi, a close friend of Ko Ni, remained silent in the wake of the incident.

On Sunday she made a rare public appearance at a memorial service organised by her party for the two victims.

"Losing U Ko Ni is a great loss for our NLD. He worked together with us for many years through his beliefs," she told a packed hall in Yangon, describing both he and the taxi driver as "martyrs".

A constitutional expert, Ko Ni was a prominent critic of the military's continued political influence including their control of key security ministries and guaranteed seats in parliament, something the NLD hopes to one day overturn. 

He also condemned the increasing Islamophobia that has swept through the nation in recent years, stirred up by hardline Buddhist nationalists.

That Suu Kyi said so little about the killing surprised some observers, but since her government took power last May after years of army-led rule, her administration has taken on something of a bunker mentality.

Suu Kyi rarely gives policy speeches, releases statements or holds press conferences.

Her young administration has had to deal with both soaring expectations of the electorate and a series of crises.

Some of the worst fighting in decades has broken out between the military and ethnic rebels, hampering her dream of forging a nationwide ceasefire.

Meanwhile the UN says security forces have "very likely" committed crimes against humanity and ethnic cleansing towards the Muslim Rohingya minority in a security crackdown last year.

Suu Kyi has defended the military's Rohingya crackdown, much to the dismay of many of Myanmar's western allies, who saw the country's transition from dictatorship to quasi-democracy as a rare success after the failures of the Arab Spring.

At the memorial, Suu Kyi stayed clear of politics but she did appeal for patience, arguing her government has only been in power for 10 months after decades of junta rule.

"Our citizens who have been struggling hard for many decades may think it's a very long time. But for the history of a country, for the history of a government, 10 months or one year is not much. This is just a short period," she said.