An Iranian man was shot dead by the security forces after celebrating when the United States eliminated his country's national team from the World Cup, rights groups said Wednesday.

Iran was knocked out of the World Cup by its arch enemy the United States in Qatar on Tuesday night, drawing a mixed response from pro- and anti-regime supporters.

Many had refused to support the national team in response to a bloody government crackdown on more than two months of protests sparked by the death in custody of Mahsa Amini.

Mehran Samak, 27, was shot dead after honking his car horn in Bandar Anzali, a city on the Caspian Sea coast northwest of Tehran, human rights groups said.

Samak "was targeted directly and shot in the head by security forces... following the defeat of the national team against America", said Oslo-based group Iran Human Rights (IHR).

The New York-based Center for Human Rights in Iran (CHRI) also reported that he had been killed by the security forces while celebrating.

There was no immediate comment on the incident from the Iranian authorities.

In an extraordinary twist, Iranian international midfielder Saeid Ezatolahi, who played in the US match and is from Bandar Anzali, revealed he knew Samak and posted a picture of them together in a youth football team.

"After last night's bitter loss, the news of your passing set fire to my heart," said Ezatolahi on Instagram, describing Samak as a "childhood teammate".

He did not comment on the circumstances of his friend's death but said: "Some day the masks will fall, the truth will be laid bare."

He added: "This is not what our youth deserve. This is not what our nation deserves."

Ezatolahi, distraught at the result, had been seen after the final whistle being comforted both by his teammates and the US players.

- Tense funeral -

Iran's team were under intense scrutiny at the World Cup, not singing the national anthem in their first match but doing so in two subsequent ones, amid reports of pressure from the authorities not to show support for the protests.

The CHRI published a video from Samak's funeral on Wednesday at which mourners could be heard shouting "Death to the dictator".

The chant aimed at Iran's supreme leader Ayatollah Ali Khamenei is one of the main slogans of the protests that flared after Amini's death in custody on September 16.

IHR said that the authorities had refused to hand the body over to the family, while BBC Persian said the funeral in Bandar Anzali had gone ahead without prior announcement and with a heavy security presence in a bid to avoid major incidents.

Iran's security forces have killed at least 448 people in the crackdown on the protests, including 60 children under the age of 18 and 29 women, according to IHR.

An Iranian general said on Monday that more than 300 people have been killed in the unrest.