The 32-year-old Luiz had signed a new two-season contract in May with Chelsea, which the center back rejoined from Paris Saint-Germain in 2016. But the Brazilian has left Stamford Bridge before playing a competitive match under new manager Frank Lampard.
Luiz played under Arsenal manager Unai Emery at PSG.
Tottenham has signed Argentina midfielder Giovani lo Celso from Real Betis on a one-year loan deal with the option to make the transfer permanent.
Lo Celso joined Betis from Paris Saint-Germain last year, initially on loan before the Spanish club signed him on a permanent basis in April.
The 23-year-old scored 16 times in 45 appearances in all competitions for Betis.
He has also played 19 times for Argentina.
Manchester City has signed goalkeeper Scott Carson on a season-long loan from Derby County.
The 33-year-old Carson will serve as an understudy to Ederson and Claudio Bravo.
Carson says: "It's something I didn't expect but an opportunity I simply could not turn down. To be part of this squad — the Champions of England — is a dream come true."
Carson, who counts West Bromwich Albion and Liverpool among his former teams, made four appearances for England.
Former England forward Andy Carroll has returned to his boyhood club Newcastle United eight years after he left.
Carroll has signed a one-year contract with Newcastle after being recently released by West Ham following a six-year spell blighted by injuries.
The 30-year-old says: "I have to bide my time, get fit, get back in the game really and work my way in."
Carroll progressed from the youth team at Newcastle, making his debut in 2006 before moving to Liverpool five years later.
Arsenal has signed Scotland left back Kieran Tierney from Celtic for 25 million pounds ($30 million).
Tierney has made 170 appearances for Celtic and the 22-year-old has played 12 times for Scotland.
Arsenal coach Unai Emery says: "He's a very talented player who will continue to improve. He increases our options defensively and I look forward to him joining our group."
Arsenal is also expected to complete a deal for Chelsea defender David Luiz before the end of Thursday's transfer window.
Watford has signed Ismaila Sarr from Rennes for a club-record fee, with the Senegal winger penning a five-year contract.
No financial details were disclosed but Watford says it is a "new club record transfer." British media reports say Watford paid Rennes more than 25 million pounds ($30 million) for Sarr, surpassing the 18.5 million pounds ($22.5 million) it paid for Andre Gray in 2017.
The 21-year-old Sarr scored 18 goals in 77 appearances for Rennes over two seasons.
Sarr helped Senegal reach the final of the Africa Cup of Nations, where it lost to Algeria last month.
Inter Milan has completed the signing of forward Romelu Lukaku from Manchester United.
The Serie A club, which is coached by former Chelsea manager Antonio Conte, confirmed the deal with a video on its Twitter account.
Wearing an Inter jersey, Lukaku says: "Inter is not for everyone, that's why I'm here."
"Not for everyone" is Inter's new international media campaign.
No financial details were disclosed but Italian media reports Inter have paid United around 65 million euros ($73 million) plus 13 million ($15 million) in add-ons for the 26-year-old Lukaku.
Manchester United forward Romelu Lukaku was in Italy on Thursday to complete his move to Inter Milan on the final day of the Premier League's transfer window.
Lukaku was having a medical at the Serie A club, which is coached by former Chelsea manager Antonio Conte.
The 26-year-old Lukaku was greeted by more than 200 fans when he arrived at Milan's Malpensa airport at 2 a.m. local time on Thursday morning.
They chanted his name and he smiled and high-fived several fans as he walked past.
Italian media reports Inter will pay United around 65 million euros ($73 million) plus 13 million ($15 million) in add-ons for the Belgium international.
Lukaku, who has been training this week with former club Anderlecht, scored 42 times in 96 matches for United after joining from Everton in 2017.
The transfer window shuts in England at 1600 GMT.
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