US tech giant Microsoft says a hacking group linked to the Iranian government has targeted a US presidential campaign.

Microsoft said in a blog post on Friday that the attack took place in August and September.

It said the group dubbed "Phosphorous" made more than 2,700 attempts to identify email accounts belonging to specific customers and carried out attacks on 241 of those accounts. Four accounts were compromised.

The company did not name the political campaign involved. But it said the group targeted accounts associated with campaign officials, government officials and journalists.

Reuters news agency said the hackers had attacked President Trump's re-election campaign.

Relations between the United States and Iran have soured following last month's drone attacks on key Saudi oil facilities, which Washington accuses Tehran of carrying out.

In June, US media reported that the US military had launched cyber strikes that targeted Iranian missile control systems.

NHK