The European Union Thursday expressed concern about rising violence linked to Venezuela's elections after the murder of a leader of the opposition, which appears poised to win control of parliament for the first time in 16 years.

"Yesterday's assassination of Mr Luis Manuel Diaz, the regional secretary of the Accion Democratica party, marks a further deterioration of an already tense situation in the run up to the parliamentary elections on 6 December 2015," the EU said in a statement.

Venezuelan First Lady Cilia Flores is a political heavyweight who steadfastly served late leader Hugo Chavez and married his successor, her longtime partner Nicolas Maduro -- who now calls her the nation's "first fighter."

Flores, 59, has been engulfed by controversy after two of her nephews were arrested in Haiti and handed over to U.S. authorities, who charged them Thursday with conspiring to smuggle cocaine into the United States.

Venezuela claimed Sunday that a U.S. Coast Guard intelligence plane violated its airspace, an allegation promptly denied by the American military branch.

The Dash 8 plane took off Friday from the Hato Rey base on the Caribbean island of Curacao and entered Venezuelan airspace close to the western Los Monjes archipelago on the Caribbean coast, Defense Minister Vladimir Padrino said in a televised address.

Venezuelan President Nicolas Maduro vowed Tuesday to respect the results of legislative elections on December 6, which opinion polls show the opposition stands to win.

"The results... will be the holy gospel to me, whoever wins, at the local level, in the state and in the country," Maduro said.

Venezuela and Guyana have agreed to return their respective ambassadors to their posts, normalizing ties after months of a bitter territorial dispute.

Venezuelan President Nicolas Maduro acknowledged that his meeting with his Guyanese counterpart David Granger at the United Nations was "tense and difficult," a statement from his Foreign Ministry read.

A British-drafted resolution aimed at scaling up European military action against migrant smugglers off Libya's coast has run into opposition from Venezuela and African countries at the U.N. Security Council, a senior diplomat said Wednesday.

The measure would allow European forces to inspect and seize ships in international waters as part of efforts to stem the flow migrants making the perilous journey across the Mediterranean to reach Europe.

A Venezuelan military plane crashed on the border with Colombia during an operation to intercept an "illicit aircraft," with the fate of the two pilots unknown, the government said Friday.

The two countries have been locked in a border conflict for a month, after Venezuelan President Nicolas Maduro ordered the closure of part of the frontier, saying some of his military were attacked during an anti-smuggling operation by Colombian paramilitaries.

The United States expressed deep concern and urged Venezuela to respect human and democratic rights Friday after opposition leader Leopoldo Lopez was sentenced to almost 14 years in jail.

Lopez, 44, was found guilty of "damage and arson, public incitement and conspiracy" during anti-government protests last year, but his supporters question the independence of Venezuelan courts.

Activists planned new protests in Venezuela on Friday after jailed opposition leader Leopoldo Lopez was sentenced to nearly 14 years in prison for inciting violence during deadly anti-government protests in 2014.

After the court decision against the popular, U.S.-trained economist, the opposition called for "peaceful" protests.

The United States is seeking a "pragmatic relationship" with Venezuela, despite their governments' differences, the top U.S. diplomat for Latin America said Wednesday.

"We are continuing discussions. Although we have differences, we are trying to have a pragmatic relationship with Venezuela," said U.S. Assistant Secretary of State for Western Hemisphere Affairs Roberta Jacobson.