* U.N. urges parliamentarians: no sit-ins or protests
* Lawmakers seek U.N. help against court set up by president
* Critics say court was intended to silence oppposition
By Paul Tait
KABUL, June 27 (Reuters) - The United Nations urged the Afghan parliament on Sunday not to take any action that might provoke unrest after election officials rejected a ruling by a specially appointed court that threw out a quarter of lawmakers elected last year.
The court, established by presidential decree after fraud-marred parliamentary elections, ordered on Thursday that 62 lawmakers elected in the September poll vacate their seats in the 249-seat house over fraud concerns.
The ruling has been condemned as unconstitutional and illegal by Afghan officials and international poll observers.
Staffan de Mistura, the U.N. special representative in Afghanistan, said the disagreement over the disputed election must be resolved in accordance with the Afghan constitution.
"Parliamentarians should act responsibly in making their constitutional demands, and not resort to sit-ins, protests or other actions which could provoke public unrest," de Mistura said in a statement.
The court was set up by President Hamid Karzai last year after weeks of infighting over the election, in which Karzai's rivals made major gains. Critics have said the court was set up to further Karzai's political agenda and silence opposition.
Lawmakers earlier sent de Mistura a letter, addressed to U.N. Secretary-General Ban Ki-Moon, asking for international assistance against the court, which they described as illegal.
The letter, a copy of which was seen by Reuters, accused Karzai of overseeing Afghanistan's laws and constitution and of "having overall domination over the electoral institutions".
It asked the international community "to assist the people of Afghanistan to protect the democratic regime and rule of law, in order (that) Afghans, as a noble and eminent nation, can live in peace and harmony free of every kind of individual oppression".
Earlier, Afghanistan's Independent Election Commission (IEC), which ran the internationally funded vote, rejected the court's findings and new election results.
"Changes in results of an election after announcing final results, and specifically after opening the parliament, are not within the authority of any organisation, including the IEC, and any action in this regard is directly contradicting the enforced laws of the country," the IEC said in a statement.
It described the manipulation of results as "unprofessional and non-transparent".
With anger growing over the court's decision, about 180 lawmakers moved a vote of no-confidence on Saturday in Afghanistan's five most senior judicial officials for advising Karzai to set up the court and for failing to stop its ruling.
It was not clear, however, whether the five members of Afghanistan's Supreme Court, including Chief Justice Abdul Salam Azimi and his deputy, Bahahuddin Baha, would indeed be removed.
The deepening political crisis comes at a worrying time for Afghanistan, with violence at record levels and NATO-led forces preparing to hand over security to Afghans in several areas at the start of a gradual process that will end with all foreign combat troops leaving by the end of 2014.
Karzai's court announced its new election findings hours after U.S. President Barack Obama detailed the beginning of a U.S. drawdown, with 10,000 U.S. troops to return home by the end of this year.
The ruling has further strained ties between Karzai's government and its Western backers. Democracy International, which deployed a large team of observers during the poll, called the court "ill-advised and illegitimate".
Karzai, re-elected after a similarly tainted presidential election in 2009, has often been accused of treating parliament as a rubber stamp. (Editing by Ron Popeski)