CNN  — 

Iran unintentionally shot down the Ukrainian plane that crashed near Tehran this week, killing 176 people, the nation’s state media reported.

The general staff of Iran’s armed forces said the crash Wednesday was due to human error. Iran targeted the passenger plane unintentionally, Press TV said.

“A sad day. Preliminary conclusions of internal investigation by Armed Forces: Human error at time of crisis caused by US adventurism led to disaster,” Iranian Foreign Minister Javad Zarif tweeted. “Our profound regrets, apologies and condolences to our people, to the families of all victims and to other affected nations.”

All the people on board the Boeing 737-800 were killed when the Kiev-bound plane crashed shortly after takeoff from Imam Khomeini Airport. The victims include 82 Iranians, 63 Canadians, 11 Ukrainians, 10 Swedes, four Afghans, three Germans and three British nationals.

Fragments of the plane had been taken to a hangar off-site to “reconstruct” it for the investigation, said Ali Abedzadeh, the head of Iran’s Civil Aviation Authority. The victims’ remains have been sent to a forensic lab for DNA testing.

Debris, including passengers' personal items, at the scene.

US Secretary of State Mike Pompeo has said Washington believes it is “likely” Iran was responsible for the downing of the Boeing 737-800 and that an “appropriate response” would come when a “final determination” is made.

CNN obtained a video that appears to show a missile strike an object in Tehran’s night sky, around the same time that the Ukrainian plane crashed early Wednesday, and separate footage that captures the moment of the crash.

The crash came just hours after Iran fired missiles at Iraqi military bases housing US troops in retaliation for a drone strike at Baghdad airport that killed Iranian commander Qasem Soleimani, who was one of Iran’s most powerful and influential military leaders.

Hours after the missile operation in Iraq, US military flights around Iranian borders increased and Iranian military officials reported seeing aerial targets coming toward Iran’s strategic centers, according to a statement released by Iranian armed forces headquarters.

Defense centers around Iran reported seeing increased radar activity which caused a heightened sensitivity in the aerial defense centers of the country, the statement reads.

The Ukrainian flight took off from Imam Khomeini Airport and came close to a sensitive Islamic Revolutionary Guard Corps military center at an altitude and flight condition that resembled hostile targeting, which led to it getting unintentionally hit, it added.

Iranian authorities are in possession of the two flight data recorders, also known as black boxes, which Prystaiko said Ukrainian investigators have seen but don’t have access to. He added that Iran was, however, cooperating, and that he expected Ukraine could “extract and analyze” the data and recordings.

The last words of the pilot were “peaceful and that everything was OK,” he said.

Prystaiko said Ukrainian investigators have access to the recording of the conversation between the control tower and the Ukrainian International Airlines crew.

The recent escalated hostilities between the US and Iran have complicated the thorny task of investigating the crash. US government investigators, for example, cannot fly into Tehran and meet with government officials without a license. That prohibition is due to longstanding sanctions rather than the most recent events, according to two US officials who spoke on the condition of anonymity.

Pompeo and Treasury Secretary Steven Mnuchin announced on Friday that President Donald Trump was authorizing yet more sanctions on Iran.

The Iranian government, which under international protocol has control of the investigation, had earlier said it would not work with the US or Boeing in the probe, but on Friday reversed its position.

If Iranian authorities are unable to reconstruct and analyze the information from the fight data recorders, they said they would seek help from international partners Russia, France, Canada or Ukraine.

Ukrainian investigators were given access to the black boxes on Friday, according to Ukraine’s foreign minister, but had yet to start examining the information, which includes recordings of communications between the pilot and Tehran flight control.

The exchange of attacks between Tehran and Washington – both on Iraqi soil – marked a dramatic escalation of tensions between the adversaries and raised fears of another proxy war in the Middle East.

A US official familiar with the intelligence said the aircraft was downed by two Russian-made SA-15 surface-to-air missiles. The US saw Iranian radar signals lock onto the jetliner, before it was shot down.

The US increasingly believes this was accidental.

The US, Britain, Canada, Sweden and the European Commission have called for an independent and credible investigation.

CNN’s Radina Gigova, Clarissa Ward, Sebastian Shukla, Jim Sciutto, Pamela Brown, Barbara Starr, Zachary Cohen and Paul P. Murphy contributed to this report