A soldier inspects the remains of one of the bombs
The blast - which severely damaged a regional office of one of the country's biggest TV and radio networks - was the third large car bomb in the city this year. No group has yet claimed responsibility.
In Marinilla, about 60km east of Medellin, another car bomb killed a woman and wounded 20 other people.
Security forces have blamed the country's second largest rebel force, the 5,000 strong National Liberation Army (ELN).
Analysts say it is too early to say whether the actions are part of a concerted effort on the part of the guerrillas to sow terror across the country.
Stalled peace talks
The ELN has been on the rampage for almost two weeks after the government broke off peace talks with the group, saying the guerrillas were not interested in a peace deal.
In the eastern province of Santander, up to 20 ELN guerrillas were blown up by their own bomb when the truck they were driving exploded.
In the north of the country, five rebels of the left-wing Revolutionary Armed Forces of Colombia, (FARC), were killed as they tried to blow up a passing army patrol.
The peace process with the FARC, which has been going on for over two and a half years, has also stagnated, and the rebels have launched a major offensive in the east of the country, where security forces are engaged in heavy combat.
Tough stance
What analysts are agreed on is that both guerrilla groups have hardened their rhetoric and escalated their attacks.
Politicians of all sides are talking tough in anticipation of the presidential elections next year, and thoughts of peace appear to be receding on all sides.
About 40,000 people have died in the past decade in Colombia's bitter 37-year long civil war.