The first two crude low-power bombs exploded near the US Embassy in Bogota shortly after the arrival in Colombia of US President Barack Obama, who is due to take part at the Americas summit in the resort city of Cartagena.
"Nobody was killed, nobody was injured, and there was no damage," a police official told AFP on condition of anonymity, and without giving any word on the suspects.
That incident occurred at around 7:30 pm local time (0030 GMT Saturday), prompting police units to swarm into the area and begin an investigation.
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These explosions were followed by two similar ones in Cartagena, which is hosting the summit.
"They occurred near a bus terminal and near a supermarket," General Rodolfo Palomino of the Colombian police told reporter. "There were no injuries and no damage."
In addition to the US Embassy, the area in Bogota where the devices exploded is home to some important Colombian government buildings.
The prosecutor general's office is located nearby as well as the so-called National Administrative Center, which houses several government ministries.
The Colombian capital and other major cities have been a favored site of urban guerrilla attacks for decades.
The Revolutionary Armed Forces of Colombia (FARC) has been at war with the Colombian government since 1964 and is believed to have 9,000 fighters in mountainous and jungle areas, according to government estimates.
In late March, Colombian troops killed at least 36 suspected FARC rebels and captured four in an army offensive in Meta department, according to officials.
The hostilities between the government and leftist rebels have continued despite solid gestures toward peace, including the recent release by the FARC of the last 10 soldiers and police held captive in the Colombian jungle.
