Clashes between Venezuela's military and armed groups have occurred near the border with Colombia since March 21.

Venezuela is preparing "to ask for immediate emergency aid from the UN... to defuse minefields left by these illegal groups of murderers and drug traffickers from Colombia," Venezuelan President Nicolas Maduro said in a televised speech.

According to Caracas' official toll, 15 people -- six Venezuelan soldiers and nine members of the armed groups described as "terrorists" by authorities -- were killed Sunday, while the Venezuelan military posted photos of artillery fire on Twitter.

More than 30 people have also been arrested, and weapons, explosives and drugs seized since the start of the fighting intended, according to Caracas, to prevent Colombian armed groups settled along the border from entering Venezuelan territory.

"We have dislodged (these groups) from several camps. They left a mined territory behind... We have lost several soldiers with these mines," Maduro said.

The socialist leader again accused the groups of ties "to the Colombian army and the government of Ivan Duque," the Colombian president.

"They are dressed as guerrillas to serve the drug trafficking routes," Maduro added.

Security sources in Colombia say the "armed groups" are dissidents of the now-disbanded Revolutionary Armed Forces of Colombia (FARC) rebel group.

The FARC signed a historic peace agreement with Bogota in 2016 to end a half century of armed conflict.

But some guerrilla fighters refused to join the peace process and have continued their struggle, while also mixing with and battling drug-traffickers in lawless areas of Colombia, including close to the Venezuelan border.

Maduro acknowledged last Sunday that it was possible the groups were FARC dissidents.

Diplomatic relations between the neighboring South American nations have been nonexistent since Colombia recognized Venezuelan opposition leader Juan Guaido as his country's interim president in 2019.

Bogota has also long accused Venezuela of shielding members of FARC and armed rebel group ELN on its soil, a charge Maduro denies.

More than 3,000 people have fled to Colombia since the fighting broke out, according to Bogota.