MEDELLIN, Colombia — Venezuela’s left-wing president, Hugo Chavez, ordered soldiers to mass on the border with Colombia yesterday, accusing American-allied Bogota of the “cowardly murder” of a senior commander of the Marxist FARC rebels, Raul Reyes. Reyes was killed by Colombian forces in an attack on a jungle camp in Ecuador on Saturday.

Mr. Chavez, who called Reyes a “true revolutionary,” ordered his country’s embassy in Bogota closed and said Colombia’s actions could spark a war in South America.

The Colombian military struck a mile inside neighboring Ecuador with bombers and helicopter-borne troops.

“Don’t think about doing that over here because it would be very serious, it would be cause for war,” Mr. Chavez, who has stated his support for the FARC and asked that it be removed from international lists of terrorist organizations, said. He added that Colombia was now acting under the orders of Washington and turning into the “Israel of the Americas.” Venezuela shares a 1,400-mile, porous border with Colombia, and guerrillas of the FARC, as well as the smaller National Liberation Army, are known to have camps and logistic networks within Venezuela.

It was the first time in 44 years of fighting that the Colombian army has managed to kill a member of the FARC’s seven-man ruling body, the Secretariat.