The Tánaiste has said that Irish citizens should not travel to Israel in the wake of the attacks on Iran.
Mr Harris said that this was an extension of advice that was already in place for Iran.
It follows strikes across Iran by Israel, which Iran described as a "declaration of war".
Israel targeted Iranian nuclear facilities, ballistic missile factories and military commanders at the start of a prolonged operation Israel says is designed to prevent Tehran from building an atomic weapon.
"We're keeping in close contact with our diplomatic teams on the ground in Iran and Israel, but I would ask all Irish citizens to heed that updated travel advice," he said.
He said Ireland had a diplomatic presence in Iran, and that Ireland was in regular contact with them.
He said that there was a small number of Irish citizens living in Iran.
"There are a small number of long-term residents in Iran who are Irish citizens, I think around 17 are known to us. We are keeping in very close contact with them too.
"But the change in advice today is please do not travel to Iran and Israel. This is an extraordinarily volatile and dangerous time, and I'd encourage all Irish citizens to heed that advice," he added.
Mr Harris said that Israel's ongoing attacks on Iran are "extraordinarily dangerous" and could not be more serious.
Speaking on RTÉ's News at One on Friday, Mr Harris said there needs to be an immediate "de-escalation" in the region and called on both sides to "step back from the brink".
He said that the way forward is through negotiations.
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Taoiseach Micheál Martin has said he is very concerned about the attack by Israel on Iran because it creates wider potential for conflict in the region.
He said there had been too much conflict in the Middle East including the war in Gaza, war in Lebanon and attacks on Iran leading to counter attacks by Iran.
"It is ordinary civilians who are bearing the brunt of this and it needs to stop and we need a re-assertion of the international rules-based order.
"We would call on all parties for restraint and to de-escalate because of the potential wider ramifications for the world and for people's livelihoods and lives," he said.
