Three suspected jihadists who were killed in a pre-dawn raid by Burkina Faso security forces had been "planning an attack" in the capital Ouagadougou, the country's prosecutor said on Wednesday.
The militants, along with a fourth who was captured, were tracked down to a house in Ouagadougou on Tuesday.
"It has been established that they were planning an attack in the capital in June against key targets," said prosecutor Maiza Sereme.
The militants also had "a link" with a brazen attack in March on Burkina's armed forces headquarters and the French embassy.
Two number plates which matched those of mopeds used in the attack were found in the house, she added.
In Tuesday's operation, a member of a gendarmerie assault unit died of his wounds and six other people - four gendarmes and two neighbours - were injured, the defence ministry said.
Police found six assault rifles, explosives and detonators, French and Burkinabe military clothing, mobile phones and SIM cards, and a notebook with writing in Arabic, it added.
Security Minister Clement Sawadogo said Tuesday's raid had targeted "suspected terrorists with a connection to the March 2 attacks."
The inhabitants of the house had "an arsenal which they used to fight back against our men... it's clear that they really were terrorists equipped to carry out missions," Sawadogo said.
Burkina Faso is in the grip of a three-year-old jihadist insurgency that has killed scores of people and driven thousands from their homes.
Ouagadougou has come under attack three times, mostly recently on March 2, when jihadists attacked the military headquarters and French embassy in a coordinated operation claimed by the so-called Group to Support Islam and Muslims (GSIM).
Eight soldiers and eight assailants were killed, and 61 soldiers and 24 civilians were injured, according to an official toll released three days later.
The anti-terror operation came eight days after the assassination of the prefect - the state's paramount representative at local level - in Oursi, a town in the far north near the Mali frontier.
Last month, the authorities in the eastern and northern border regions arrested around 100 people and seized explosives.
In the previous attacks in Ouagadougou, in January 2016, jihadists attacked the city's Splendid Hotel and a cafe, leaving 30 dead, around half of them foreign nationals.
In August 2017, two young gunmen opened fire on people at a Turkish restaurant just metres (yards) away from the Splendid Hotel, killing 19 people, at least eight of them foreigners.