Manchester City increased the pressure on Mikel Arteta as the League Cup holders powered into the semi-finals with a 4-1 demolition of troubled Arsenal on Tuesday.

City ensured it will be a miserable Christmas for beleaguered Arsenal boss Arteta by condemning his side to a fourth defeat in their last six games in all competitions.

Gabriel Jesus took just three minutes to put City ahead at the Emirates Stadium and although Alexandre Lacazette equalised, it was another night of torture for Arteta.

Arsenal's reserve keeper Alex Runarsson was made a horrendous mistake when he allowed Riyad Mahrez's free-kick to squirm into the net.

Phil Foden and Aymeric Laporte piled on the pain for Arsenal with further goals to seal the rout.

"It's a hard one to take considering how the game went. This level of opponent, when you give the goals away it makes the game impossible," Arteta said.

"A lot of strange things are happening in every game and that makes things really difficult.

Brentford's Josh Dasilva celebrates his goal against Newcastle
Brentford's Josh Dasilva celebrates his goal against Newcastle POOL / HANNAH MCKAY

"Runarsson has not played a lot of games for us. We all make mistakes and have to support him."

Languishing 15th in the Premier League after losing five of their last seven games -- their worst start to a season since 1974-75 -- Arsenal are in crisis.

Amid talk of dressing room unrest, Arteta, who worked as Pep Guardiola's City assistant before joining Arsenal 12 months ago, will be in danger of the sack if Arsenal's wretched run continues into the new year.

"We have to turn it around. If we don't, we are in big trouble. So that is the moment which is going to decide our season," Arteta said.

"On the basis of what we have shown tonight against difficult opponents, I have fighters in my team."

Guardiola defended Arteta, saying: "He is an incredible manager. I know his proposals and what he will do.

"Not even a little run of bad results is going to change my opinion."

Manchester City striker Gabriel Jesus celebrates scoring against Arsenal
Manchester City striker Gabriel Jesus celebrates scoring against Arsenal AFP / Adrian DENNIS

Arteta made eight changes from Saturday's defeat at Everton, yet City made seven switches of their own and still went ahead in the blink of an eye.

Jesus, without a goal in his previous seven games, started the move wide on the left when he fed Foden and made an astute run into the six-yard box.

Oleksandr Zinchenko's cross reached Jesus and, aided by Runarsson's missed punch, the Brazilian netted with a clinical header at the near post while the Gunners' defence stood and watched.

Arsenal equalised against the run of play in the 31st minute as Gabriel Martinelli's cross from the byline found Lacazette, who threw himself forward to guide his header into the roof of the net.

City were gifted the lead again in the 54th minute when Runarsson made a complete hash of dealing with Mahrez's free-kick, the Iceland international allowing a shot that was straight at him to slip through his gloves like a bar of soap.

With no VAR in the League Cup, Foden's run from a slightly offside position went unchecked and he delivered the knockout blow with a cool flick over Runarsson.

Foden turned provider in the 73rd minute with a teasing cross that was headed in by Laporte.

City trail eight points behind Premier League leaders Liverpool, but they are unbeaten in their last nine games in all competitions -- conceding just two goals in that period.

Guardiola's men have won the League Cup for the last three seasons and are bidding to become the first team to win it four years in a row since Liverpool from 1981 to 1984.

Brentford, fourth in the Championship,enjoyed a shock 1-0 win against Premier League side Newcastle thanks to Josh Dasilva's 66th minute goal in west London.

Thomas Frank's team had already knocked out West Bromwich Albion, Southampton and Fulham en route to the quarter-finals.

Their fourth Premier League scalp took them into their first ever major domestic cup semi-final.

"I'm bitterly disappointed and very frustrated at this minute," Newcastle manager Steve Bruce said.