Venezuela tightened security at embassies Wednesday after two bombs ravaged Colombian and Spanish diplomatic missions, injuring four people and generating fears that the nation's political crisis was entering a more violent phase.

The United States, Colombia and other nations demanded a swift investigation into Tuesday's bombings, which came 15 minutes apart at the Spanish embassy and Colombian consulate.

Venezuela suggested the bombings were meant to destabilize the government of President Hugo Chavez, who on Sunday criticized Spain and Colombia for allegedly interfering in Venezuelan affairs.

"There are elements thinking of taking the route of terrorism" to oust Chavez, said Vice President Jose Vicente Rangel.

Chavez had just weathered a two-month strike seeking his ouster and has vowed that strike leaders, including prominent business and labor chiefs, will be prosecuted. Colombia and Spain expressed concern over the arrest of Carlos Fernandez, head of Venezuela's largest business chamber.

Rangel announced the creation of an anti-terrorism task force and played down the importance of pamphlets left at the bombing sites swearing allegiance to Chavez and his so-called "Bolivarian revolution."

The attackers, Rangel said, merely neglected "to leave Chavez's photo" to implicate the president. Rangel expressed Venezuela's solidarity with both Colombia and Spain.

Interior Minister Lucas Rincon said C-4 plastic explosive may have been used in the pre-dawn blasts, which also damaged stores and apartment buildings.

Spanish Ambassador Manuel Viturro de la Torre refused to speculate on a motive for the attacks. Colombia used the incident to request Venezuela's cooperation in its decades-old war against leftist Colombian rebels, whom Bogota said often seek haven in next-door Venezuela.

On Sunday, Chavez criticized several nations for their concerns about Fernandez's arrest. He also singled out Cesar Gaviria, secretary general of the Organization of American States, who has spent three months trying to mediate a solution to Venezuela's conflict.

Gaviria was returning to Caracas to resume those talks Wednesday.

In Washington, State Department spokesman Philip T. Reeker condemned the bombings, saying they underscored the need for all sides to honor a Feb. 18 nonviolence pledge, refrain from "confrontational rhetoric" and create a truth commission to investigate violent incidents.

"We note that those bombs follow some sharp verbal attacks by President Chavez on the international community, as well as individual Venezuelans and institutions," Reeker said.

The Atlanta-based Carter Center, co-sponsor of the peace talks, urged all sides — including Venezuela's opposition news media — to abandon hate-filled rhetoric that has stoked tension this South American nation.

"We call on the leadership of the country to hear the demand of the Venezuelan people for reconciliation and an end to violence in their country," the center said in a statement.

Former President Jimmy Carter has supported Gaviria's efforts to broker an electoral solution.

Chavez, elected to a six-year term in 2000, accuses Venezuela's traditional elite of seeking his ouster and foiling his efforts to distribute Venezuela's oil riches to the poor.

His opposition accuses the former army paratrooper of imposing an authoritarian regime and ruining the economy.

Fernandez, the business leader, faces rebellion and other charges for leading the 63-day general strike against Chavez. Police are searching for strike co-leader and labor boss Carlos Ortega.

The strike, which ended Feb. 4, hobbled the world's fifth-largest petroleum exporting industry and robbed the feeble economy of billions of dollars.