* Kuwait has so far avoided "Arab Spring"
* Political crisis has held up development plans
* Opposition warns against "aggression" towards march
By Ahmed Hagagy
KUWAIT, Oct 20 (Reuters) - Opposition groups in Kuwait say they will boycott Dec. 1 parliamentary elections, calling changes to the voting system announced by the government on Saturday a "coup against the constitution".
Kuwait has been torn by a power struggle between the government, controlled by the ruling Al-Sabah family, and the elected parliament. The turmoil has blocked development plans and paralysed the political system.
The Kuwaiti government, at an extraordinary meeting in Kuwait city of Saturday, ordered elections to held on Dec. 1, and decided to amended the election law to allow each voter to choose only one candidate instead of four.
The opposition, including Islamists, liberals and tribal figures who won a majority in the 50-seat parliament in the last election in February, rejected the changes and called for a protest march on Sunday, said Ahmed al-Dayen, an opposition politician.
Kuwait's oil wealth and a generous welfare state have helped it avoid the "Arab Spring" protests that forced out leaders elsewhere in the region. But there have been regular demonstrations in the country since last year.
Opposition leaders, meeting at a guest house owned by former parliament speaker Ahmed al-Saadoun, blamed the government for the political crisis and warned it was driving the country towards "autocratic rule".
"We call on the proud and free people of Kuwait to ... boycott the upcoming election, both by (refraining) from running in it or casting ballots," a statement after the meeting said.
It asked Kuwaitis to join a protest march on Sunday, and warned the interior minister against committing "aggression" against it. "We will hold him personally responsible for that," the statement said.
Sheikh Sabah al-Ahmad al-Sabah, Kuwait's emir, dissolved parliament on Oct. 7, and under Kuwait's constitution elections are supposed to be held within 60 days.
It was the sixth dissolution of parliament since early 2006 in the oil-rich state, an ally of the United States.
Sheikh Sabah, in a televised speech on Friday night, instructed the government to change the election law in what he said was a move to stem recurring crisis. He also said the constitutional court had issued a ruling that allowed for any necessary changes to be made to the country's electoral system.
Kuwaiti authorities arrested two opposition politicians on Thursday and interrogated a third after they made comments seen as criticizing the emir.
The former members of parliament spoke at an opposition-led rally of about 5,000 people on Monday, at which Kuwaitis later clashed with riot police close to parliament.
The arrests have prompted protests in Kuwait, including one late on Friday, when some 1,000 people had gathered in the centre of the capital to demand the release of the detainees.
The events prompted the Al-Sabah family to issue a rare statement on Thursday calling for obedience to the emir.
The Al-Sabah dynasty has ruled Kuwait for more than 250 years. The 83-year-old emir has led the country since 2006.
Although Kuwait allows more freedom of speech than some of its fellow Gulf states, the emir is seen as untouchable and is referred to as "immune and inviolable" in the constitution.
Sheikh Sabah warned in his speech on Friday the recent political turmoil in Kuwait could lead to "strife that could be about to erupt and destroy our unity, disfigure our identity and tear apart our society into fragmented groups".
He said he had instructed the government to establish a national electoral committee and to organise election campaigns "to guarantee the integrity of the electoral process."