The Republic of Ireland's World Cup qualifying hopes suffered a major blow as they fell to a dismal but deserved defeat by Armenia in Yerevan.

Three years on from a shock Nations League loss to the same opponents, the Republic of Ireland were again humbled by a side ranked 105th - 45 places below them - in the world.

Eduard Spertsyan - who scored the winner in 2022 - put Armenia ahead from the penalty spot in first-half stoppage time after Republic of Ireland captain Nathan Collins fouled Lucas Zelarayan.

The away side's woes deepened when Grant-Leon Ranos doubled Armenia's lead six minutes into the second half.

While Evan Ferguson quickly pulled a goal back, the Republic of Ireland were spared further embarrassment when Artur Serobyan's late strike was ruled out for offside.

After a home draw with Hungary in Saturday's opening qualifier, Tuesday's result will serve as a hammer blow for Republic of Ireland boss Heimir Hallgrimsson's hopes of leading the team to their first World Cup since 2002.

The Irish started the game brightly, with Ferguson's lobbed effort headed off the line by Erik Piloyan after Armenia keeper Ognjen Cancarevic spilled the ball and was left stranded.

Jack Taylor, who replaced the injured Sammie Szmodics in the visitors' line-up, was also denied when Cancarevic saved his low shot at the near post.

But Armenia grew into the game, and after Ranos rattled the crossbar, Spertsyan drove his penalty past Caoimhin Kelleher, who was beaten for the second time when Ranos pounced on Nair Tiknizyan's cross early in the second half.

Worryingly for Hallgrimsson, Ferguson's fine sweeping finish was the only moment of quality his players mustered in the final third in response.

Now, with one point from two games and a couple of daunting Group F matches against Portugal still to come, Irish hopes of ending their long wait for a return to football's biggest stage are already hanging by a thread.

In their last World Cup qualifying, the Republic of Ireland's second game ended in an embarrassing home defeat by Luxembourg - then ranked 98th - in March 2021.

While Tuesday's loss was not inflicted on home turf, it is equally chastening - and certainly as disastrous for the team's aspirations of returning to football's biggest stage.

Like the infamous Luxembourg game, the Republic of Ireland produced a woeful performance in Yerevan, with Armenia - thrashed 5-0 by Portugal on Saturday - richly deserving their win after continuously cutting Hallgrimsson's side apart.

Having fought back from two goals down to draw with Hungary, the Republic of Ireland should have had a spring in their step on Tuesday.

The opposite was true. While they started well and could have scored an early opener through Ferguson, they quickly ceded control and never regained it after conceding first for the ninth time in Hallgrimsson's 10th competitive game in charge.

Outside of Ferguson's goal, the Republic of Ireland rarely troubled the Armenian defence. Taylor and Chiedozie Ogbene, the two players drafted into the starting line-up, were taken off by Hallgrimsson at half-time, with even the introduction of Adam Idah three days after his late leveller against Hungary failing to spark them into life.

It could have been worse from an Irish perspective, too, had it not been for a couple of impressive Kelleher stops and a video assistant referee intervention cutting Serobyan's celebrations short.

Hallgrimsson may argue that, with four games to come in this campaign, there is still time for his side to turn things around.

But on Tuesday's evidence, this Irish team do not stand a chance of getting anything from next month's trip to Portugal, leaving them needing an unlikely combination of results if they are to earn a spot in the play-offs.

In addition to that five-goal thrashing by Portugal last weekend, Armenia's recent results include a 5-2 friendly loss to Kosovo and a 9-1 aggregate defeat by Georgia in their Nations League relegation play-off in March.

But against the Republic of Ireland, they looked comfortably superior in all areas and will probably wonder how they did not score more after having regularly troubled the visitors' defence.

Ultimately, it did not matter. Armenia can now savour a famous win and will be confident of securing a result when they visit Dublin next month, while Hallgrimsson - like his predecessor Stephen Kenny - will face difficult questions about his future after a demoralising start to the campaign.

Republic of Ireland boss Heimir Hallgrimsson, speaking to RTE: "Today I take the blame for this. Of course I take the blame for this, but the players are the same players we were happy with against Bulgaria and in the second half against Hungary.

"So, as I said, it is an off day and we have to look inside and see what we can do differently."

On his future: "The job of the coach, if they are not producing, then of course it is always a question.

"I am not naive, it is understandable now and after this performance. I will take the blame, the players need support and we need to encourage them."

Armenia: Yegishe Melikyan's side travel to Hungary on 11 October before a visit to Dublin to face the Republic of Ireland three days later.

Republic of Ireland: Hallgrimsson's team face a daunting trip to group favourites Portugal on 11 October before attempting to avenge Tuesday's loss against Armenia.