YANGON - A prominent Muslim lawyer and member of Myanmar's ruling party was shot dead along with a taxi driver outside Yangon's international airport on Sunday, officials said.

Ko Ni, a legal advisor to Aung San Suu Kyi's National League for Democracy (NLD) party, was gunned down as he got into a taxi outside arrivals around 5pm (1030GMT) by an assassin who also killed the driver.

"According to our initial information, Ko Ni and the taxi driver were killed," a security source at the airport told AFP, asking not to be named. "An unknown man shot him in the head while he was hiring a taxi. He was later arrested," the source added.

Zaw Htay, a spokesman at the president's office, said Ko Ni had just returned from a government delegation trip to Indonesia. "He (Ko Ni) was shot while he was waiting for a car outside the airport. Ko Ni died on the spot," he told AFP.

There were no reports on possible motives behind the murder but the daylight slaying will do little to calm already heigtened nerves within Myanmar's Muslim community.

Myanmar's border regions have simmered for decades with ethnic minority insurgencies. But it is rare for prominent political figures to be murdered in Yangon, the country's booming and largely safe commercial hub.

However in recent years Myanmar has witnessed a surge of anti-Muslim sentiment, fanned by hardline Buddhist nationalists.

Ko Ni, a legal advisor to the NLD, was a rare voice advocating religious tolerance and pluralism.

In late 2015 Suu Kyi's NLD party won a landslide election victory, ending decades of military-led rule.

But in what analysts widely saw as a sop to Buddhist hardliners the party fielded no Muslim candidates, despite boasting many senior Muslim figures in its ranks.

Suu Kyi has also faced international censure for her failure to criticise an ongoing army crackdown against the Muslim Rohingya minority in western Rakhine state.

Since the launch of the crackdown in October at least 66,000 Rohingya have fled to neighbouring Bangladesh alleging security forces are carrying out a campaign of rape, torture and mass killings.

The treatment of the Rohingya, a stateless group denied citizenship in Myanmar, has galvanised anger across the Muslim world.

Many among Myanmar's Buddhist majority call them Bengalis - shorthand for illegal immigrants from neighbouring Bangladesh - even though many have lived in Myanmar for generations.

Yanghee Lee, the UN's special rapporteur for Myanmar, voiced her outrage over Ko Ni's killing, saying she had met him on her last trip to the country earlier this month, which included a visit to Rakhine.

"My deepest and most sincere condolences to the family of U Ko Ni the most prominent and respected Muslim lawyer of Myanmar," she tweeted, calling on Suu Kyi's government to "get to the bottom" of his death.