The Gunner dispatched Bournemouth 3-0 earlier in the day but Haaland's first-half hat-trick, including two penalties, started a roaring response from City at Etihad Stadium.

Haaland added his fourth after the interval before Julian Alvarez wrapped up the scoring, with Hwang Hee-Chan's second-half strike a mere consolation in a 5-1 hammering of Wolves.

Victory extended City's unbeaten run in the Premier League to 20 games, while it has won each of the past six in a row, netting four or more goals on five occasions in that run.

Moving just a point with Arsenal and still boasting a game in hand, Guardiola was relieved to see a firing return to form for Haaland, whose April was hampered by injury issues.

"It looks comfortable but it was not," the City manager said. "In the end we created more chances but in the transition we were not precise in the last pass.

"But Erling is back to business. Penalties are a guarantee but the second and fourth [goals] were unbelievable.

"The 20 minutes he [Haaland] played against Nottingham Forest was really good and today as well. We won, but it was so long an injury.

"It is welcome he arrived in the right moment, but we arrive together because Erling and Kevin [De Bruyne] have been out."

Having scored a hat-trick in this exact fixture last season, Haaland became just the third player to score a home treble against the same opponent in consecutive Premier League campaigns.

The Norway talisman also became the third player to score multiple first-half hat-tricks in Premier League history (also against Nottingham Forest last season), along with Andrew Cole and Michael Owen (two each).

Yet the City forward appeared somewhat annoyed with his late substitution for Alvarez.

"He's a little bit frustrated, but I understand," Guardiola added. "He was frustrated with the referee. With the long balls sometimes they push him and he is pulled. Yes, it is like that."

City will play its game in hand against Tottenham Hotspur on 15 May (AEST), with that game representing its chance to move clear of Mikel Arteta's side.

Guardiola insists his team must win all its remaining fixtures to lift the top-flight trophy once more.

"Goal difference is not possible, we cannot draw," he added. "The way Arsenal have been playing has been so good and consistent.

"It's three games, hopefully we win the first and the second and arrive to the third with our destiny in our own hands."