By Luis Jaime Acosta and Nelson Bocanegra

BOGOTA (Reuters) -Colombia's violence took a new turn on Tuesday as a series of bomb attacks rocked the nation's southwest, while Senator Miguel Uribe continued fighting for his life days after being shot in the head during a campaign rally.

The incidents have shaken the nation and harkened back to the decades of fear and violence residents lived under caused by armed guerrillas, paramilitary groups and drug traffickers.

The explosions left at least seven people dead and more than 50 wounded, authorities said. While bomb attacks are not uncommon in Colombia, Tuesday's came on the heels of the assassination attempt on Uribe, a member of the opposition right-wing Democratic Center party and a potential presidential contender.

Uribe, 39, was shot at a campaign event in a public park on Saturday in capital Bogota. He remains in critical condition, the hospital treating him said on Tuesday.

"No family in Colombia should be going through this," Uribe's wife, Maria Claudia Tarazona, told reporters outside the hospital. "There is no name for this - it's not pain, it's not horror, it's not sadness."

Authorities said on Monday that they were investigating several lines of inquiry in the motive for Uribe's shooting. A teen has been arrested, and President Gustavo Petro said the suspect had given his testimony to police.

In a video of the teen's capture, independently verified by Reuters, he can be heard shouting that he had been hired by a local drug dealer.

In an earlier video as the suspect, who had been wounded, attempted to escape the scene, a voice can be heard shouting, "I did it for the money, for my family." Reuters also verified the video.

The suspect on Tuesday rejected charges of attempted murder and illegal possession of a firearm, the attorney general's office said. He faces up to eight years in a rehabilitation center, not prison, as he is a minor.

Petro has broadly pointed the finger at an international crime ring as being behind the attack on Uribe, without providing details or evidence.

The explosions on Tuesday were likely caused by a guerrilla group that splintered from the Revolutionary Armed Forces of Colombia (FARC) rebels, according to the army and police.

Interior Minister Armando Benedetti suggested there may be a link between the incidents, as the rebels have increasingly turned to drug trafficking to finance their activities, though he did not provide evidence.

Petro has ordered beefed-up security on government officials and opposition leaders in response to the attacks.

Uribe had been a staunch critic of Petro's security strategy aimed at ending six decades of armed conflict, arguing that Petro's approach of pausing offensives on armed groups despite the failure of peace talks only backfired.

The senator had two government-provided bodyguards protecting him at the time of the shooting, the head of the National Protection Unit said on Monday. Uribe's lawyer, Victor Mosquera, said he had repeatedly asked for more.

(Reporting by Luis Jaime Acosta and Nelson Bocanegra; Additional reporting by Kylie Madry and Inaki Malvido; Editing by Chizu Nomiyama and Leslie Adler)