PHNOM PENH (Reuters) -- Over 120 newly elected Cambodian members of Parliament met under the same roof for the first time on Saturday for a Buddhist swearing-in ceremony hosted by the king, who is seeking to end a two-month old post-election impasse.

The war-scarred southeast Asian nation's parliament officially opened a week ago, but only the ruling Cambodian People's Party (CPP) of long-term Prime Minister Hun Sen attended.

The opposition Sam Rainsy and royalist FUNCINPEC parties boycotted the parliamentary session opening in protest at what they say were unfairness and bias toward the CPP in the July 27.

The CPP won 73 seats in the elections, but fell short of the two thirds majority needed to run the country on their own.

Both Sam Rainsy and FUNCINPEC, the CPP's junior partner in the previous administration, have refused to join any coalition led by Hun Sen -- a former Khmer Rouge soldier who has been in charge for nearly 20 years.

After the half-empty opening, revered King Norodom Sihanouk -- who brokered a coalition after a similar stalemate in 1998 led to mass riots -- offered to try and bring the three sides closer together with Saturday's swearing-in ceremony.

Wearing starched white jackets and traditional purple pantaloons, the lawmakers gathered in the ornate royal throne room to take an oath of honesty and to serve to the country.

But in a sign unlikely to be seen as a good omen, a planned outdoor photo-call on the palace steps was cut short by an enormous thunder storm which rolled in across the Mekong River.