In the other semi-final, Spain's Real Betis take a 2-1 lead into the return fixture against two-time runners-up Fiorentina.

First-half goals from Jadon Sancho and Noni Madueke put Chelsea in control in Sweden, before Nicolas Jackson grabbed a brace midway through the second period.

Enzo Maresca's side have one foot in the final of the Conference League in their debut campaign in the third-tier European competition.

Lifting the trophy in the Polish city of Wroclaw on May 28 would add another continental title to the London club's haul of two Champions Leagues, a pair of Europa Leagues and two UEFA Cup Winners' Cups.

Their opponents, on the other hand, don't quite boast the same European pedigree, and in making the last four became the first Swedish side to play a semi-final in Europe since 1986/87.

To further add to Djurgarden's underdog status, coach Jani Honkavaara only had 14 senior players fit to call upon for the visit of the Premier League giants.

Chelsea took the lead via Sancho on 12 minutes as the winger collected a lofted pass in the box and slotted the ball past the goalkeeper before the retreating Marcus Danielson sliced his attempted clearance against his own arm and into the goal.

The goal settled Chelsea, who slowly got more accustomed to the artificial surface in Stockholm and began to dominate Djurgarden.

Madueke made that dominance pay two minutes prior to half-time when he opened up his body to feint a cross-goal shot with his left foot, before sweeping a first-time finish inside the near post.

- Jackson at the double -

As the interval loomed, Djurgarden nearly caught Chelsea with a sucker-punch, only for the English club's Swedish-born 'keeper Filip Jorgensen to readjust brilliantly and tip Tokmac Nguen's deflected strike behind for a corner.

Jackson put Chelsea three goals to the good one minute before the hour as he tapped in from close range following a defensive mix-up.

The Senegalese striker doubled up six minutes later, unleashing a fizzing shot with his left foot from the edge of the box.

Teenager Isak Alemayehu Mulugeta snatched a consolation for Djurgarden in the 68th minute with a powerful downward header for his first senior goal.

In Andalusia, Betis had a dream start when Abde Ezzalzouli smashed the ball in off the crossbar on six minutes following battling centre-forward play by the in-form Cedric Bakambu.

Fiorentina came within a whisker of equalising midway through the first half, but Rolando Mandragora's powerful header zipped inches wide of goalkeeper Fran Vieites' upright.

Former Barcelona centre-half Marc Bartra had a chance to double Betis' lead at the end of the first period but blasted over from a corner.

Manchester United loanee Antony then did get a second for the hosts with a fierce right-footed effort from outside the box which flew beyond David de Gea's reach and into the top corner in the 64th minute.

Fiorentina halved the lead against the run of play with 17 minutes remaining as Luca Ranieri slotted home after being teed up by Robin Gosens.

The second leg ties will take place next Thursday.