Just after the break, Isak also played a major role in what could be a decisive second goal in the tie.

This time, the Newcastle striker's quick feet allowed him to get a shot off that was parried by David Raya into the path of the onrushing Gordon, who fired in the rebound.

Arsenal should still have made its mammoth task for the return leg in Tyneside next month a more manageable one.

Havertz somehow miscued a header wide, with the goal gaping, to cut the arrears.

Howe replaced Isak and Gordon, with Newcastle happy to just to protect its lead in a 5-5-0 formation for the final 20 minutes.

Isak has been virtually unstoppable of late, and he has now scored 10 goals in his last nine appearances for the club.

The Swede lofted one early half-chance over the crossbar, but showed how lethal he is with his 37th-minute blast.

It brought up the 25-year-old's half century in just 89 matches for the club.

"In the first half he was electric, I thought he played really well. He scored, but I just thought his general game was in a really good place," Newcastle manager Howe said.

"We played with real confidence and belief, but the tie is still very much alive, and we have a really tough home leg to come."

Howe said he was proud of the way his team defended.

"There was a lot of fatigue in the second half. We knew what was at stake, and the players put their bodies on the line."

Arsenal was unbeaten in 13 games in all competitions, and is second in the Premier League standings.

Arsenal, who had 23 shots to Newcastle's seven, piled on the pressure late on to try to reduce the deficit, but Newcastle manned the barricades to take a healthy lead back home to St James' Park.

"It's about scoring goals," Arteta said.

"Credit to them, they defended their box very well. We had the chances, but at this stage, a semifinal, you have to be clinical."

Agencies