(Adds comments by U.N. spokesman, paragraph 9)
UNITED NATIONS, April 13 (Reuters) - Western Sahara's independence movement rejected on Monday a Moroccan charge that it had violated a ceasefire with a demonstration last week, saying the protest was peaceful.
Morocco had blamed Algeria for what it called a "serious and blatant" violation by the Polisario Front movement on Friday of an 18-year-long cease-fire in the disputed Northwest African territory and urged the United Nations to intervene.
Some 1,400 supporters of the Algeria-backed Polisario, including foreigners, crossed the border from Algeria into a closed military zone where they uprooted barbed wire and fired shots in the air, the Moroccan Foreign Ministry said.
But Polisario, in a letter handed on Monday to the U.N. Security Council, said that "contrary to the official and public allegations of Morocco, it was not a military activity or action. It was a huge peaceful demonstration."
The protesters "did not fire a single shot," said the letter signed by Polisario's U.N. representative, Ahmed Boukhari. He said Rabat had "deliberately distorted" the incident "to present it as a breach of the ceasefire."
Rabat and the Polisario Front have often accused one another of breaching the U.N.-supervised military truce in the phosphate-rich former Spanish colony, abandoned by Madrid in 1975 and then annexed by Morocco.
Morocco accused Algeria and Polisario of trying to scuttle efforts to forge a peaceful solution to the conflict before a U.N. Security Council meeting on the dispute later this month.
Boukhari said Morocco was "certainly in no good position to request the United Nations to shoulder any responsibility after it has sabotaged all efforts" by the organization to resolve the conflict.
U.N. spokesman Farhan Haq said Morocco had also written to the Security Council on the issue. Haq told reporters the small U.N. military observer mission in Western Sahara was trying to establish details of what had happened on Friday.
U.N.-mediated talks over the territory began two years ago but are deadlocked over whether Sahara should be an autonomous part of Morocco, as Rabat proposes, or hold a referendum on whether to become independent, as Polisario wants.
Boukhari called on Morocco to resume negotiations "with an open spirit, in good faith and without preconditions."
The letter confirmed reports that several participants in Friday's demonstration were wounded when a Moroccan antipersonnel mine exploded, and one of them lost his foot.
It called on Morocco to give the United Nations information to allow the mapping and deactivation of what it said were about 5 million such mines planted by Morocco. (Reporting by Patrick Worsnip; editing by Anthony Boadle)
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