The Red Devils wrapped up a deal to sign Lukaku from Everton last week as they secured the signing of the striker in a big-money deal.
His arrival at Old Trafford followed the capture of defender Victor Lindelof from Benfica last month.
Manchester United are thought to still be on the lookout for a number of new signings this summer as the Red Devils prepare for a return to the Champions League next season.
And Mkhitaryan says he was delighted to see the duo put pen to paper on contracts with the Red Devils this summer.
Speaking to Sky Sports, Mkhitaryan said: “I’m very pleased, I’m very happy that they have joined Manchester United, they are very good football players and it is not just like that they are here. It means they are strong enough to play for this team.
“Of course we are going to help them to settle down and adapt themselves to help us win the games.”
Manchester United are gearing up for Jose Mourinho’s second season in charge at Old Trafford following his appointment back in May of last year.
The Red Devils enjoyed a relatively successful first campaign under the Portuguese coach, as they won the EFL Cup and Europa League trophies.
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