Ecuador said on Monday it had sued Colombia in international court over drug crop fumigation along its border in a move that could stoke tensions as the neighbours spar over a Colombian raid into Ecuador's territory.

A March 1 Colombian attack on a Colombian rebel camp in Ecuador killed more than 20 people including a top guerrilla leader. It also frayed diplomatic ties and briefly raised the threat of war after Ecuador and Venezuela moved troops to their borders with Colombia.

Ecuador's legal claim, which could take years to be resolved in the International Court of Justice in The Hague, will likely delay a swift solution to the dispute. Bogota rejected Ecuador's charge.

In the latest border incident, Colombia said, an Ecuadorean army helicopter violated Colombia's airspace on Sunday and was forced to land, but then took off and flew back into Ecuador.

Tensions between the Andean neighbours remained high after Quito accused Bogota of waging a smear campaign to tie Ecuadorean President Rafael Correa to the leftist rebels.

"Ecuador asks the court to declare Colombia's air fumigation a violation of Ecuador's sovereignty," Foreign Minister Maria Salvador told reporters in Quito.

The minister demanded Colombia halt all fumigation near the border and pay the government compensation for more than seven years of spraying to destroy illicit coca crops used to make cocaine.

In a presidential statement, Colombia rejected the claim and said it had already agreed not to spray along the frontier and instead use manual eradication to attack coca crops, which it said were mainly controlled by leftist FARC guerrillas.

Colombia is the world's top producer of cocaine. Financed by billions of dollars in U.S. aid, Bogota has used aerial spraying to attack coca crops that help fuel Colombia's four-decade-old conflict. Its neighbours often charge Colombia fails to stop violence from spilling over its borders.

Correa and Colombian President Alvaro Uribe had eased tensions during a regional summit a week after the March 1 raid. But the later confirmation that an Ecuadorean was killed in the attack on the rebel camp has enraged the leftist leader.

"A solution to the diplomatic row seems far off for now," said Felipe Burbano, an analyst with Ecuador's branch of the Latin American Faculty of Social Sciences. "Ecuador is taking the dispute to another level."

Colombia charges a top Correa cabinet member had links with Marxist rebels and says Ecuador does little to help protect its porous 400-mile (600 km) border, which guerrillas have often crossed over to organize attacks on Colombia.

Ecuador says Colombian fumigation hurts legitimate crops and the health of Ecuadorean farmers living along the border. Colombia rejects the charges and says spraying is safe.