SINGAPORE/KIEV (Reuters) - Five countries whose citizens were killed when an airliner was shot down by Iran last week will meet in London on Thursday to discuss possible legal action, Ukraine’s foreign minister told Reuters.

Speaking on the sidelines of an official visit to Singapore on Monday, Vadym Prystaiko said the five nations would also discuss compensation and the investigation into the incident.

All 176 people on board the Ukraine International Airlines flight were killed in the crash on Wednesday, minutes after the plane took off from Tehran airport.

In Kiev, Ukraine’s top security official said a senior Iranian investigator would visit the Ukrainian capital in the coming days to determine whether a Ukrainian laboratory is suitable to decode the plane’s black box flight recorders.

Prystaiko said suggestions from Iran that the plane was shot down as it flew near a sensitive military base during a time of heightened tensions were “nonsense”.

“We have created this group of foreign ministers from the grieving nations. On Jan 16, we will meet in person in London to discuss the ways, including legal, how we are following this up, how we are prosecuting them (Iran),” Prystaiko said.

He said the five nations also included Canada - which had at least 57 passport holders aboard the doomed flight - Sweden, Afghanistan and a fifth country which he did not name. Canada has previously said these four countries and Britain had established a coordination group to support victims’ families.

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Many on board were Iranians with dual citizenship.

After days of denials, Iran said on Saturday its military had shot down the plane in a “disastrous mistake”.

Tehran said its air defenses were fired in error while on alert after Iranian missile strikes on U.S. targets in Iraq, and that the airliner was mistaken for a “hostile target” after it turned toward a sensitive military base of the elite Revolutionary Guards near Tehran.

“This is nonsense because our plane was recorded and confirmed - was going within the international route which was given by the dispatchers...Nothing was extraordinary,” Prystaiko said, adding that investigators said the pilot’s last words were “everything is ok on board and I am switching to auto pilot.”

“I have seen this information on media that our plane changed the route...Yes, because it was hit by rocket! It was already dying.”

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EXPLANATION FOR EARLY CONFUSION

Oleksiy Danylov, secretary of Ukraine’s national security and defense council, told Reuters in Kiev that Iran would have the final say on where the black box recorders would be decoded.

Danylov also offered an explanation for an early source of confusion: a statement issued by Ukraine’s embassy in Iran on the day of the crash that initially pointed to engine failure as the cause.

The statement, which was deleted later that day and replaced with another statement saying the cause was unknown, had been issued to try to gain access to the crash site, Danylov said.

“If we had said straight away that they had shot it down, I am not sure they would have let us go to the wreckage at all, let us do what we were doing,” he said.

Iran’s Revolutionary Guards apologized to the nation and accepted full responsibility. Senior Guards commander Amirali Hajizadeh said he had informed Iran’s authorities last Wednesday about the unintentional strike, a comment that raised questions about why officials had publicly denied it for so long.

Prystaiko said all involved had to be held to account and that Ukrainian investigators should be central to the investigation.

“We have to dig out who gave the order, who pushed the button. Everything...all these people should be punished,” he said.