West Ham have signed Nottingham Forest winger Michail Antonio and Hull striker Nikica Jelavic and completed loan deals for Barcelona midfielder Alex Song and Chelsea winger Victor Moses.
Antonio, 25, has moved to the Hammers for an undisclosed fee, reported to be £7m, while 30-year-old Jelavic moves in a transfer worth about £3m.
Song, 27, and Moses, 24, have joined the club on season-long loan deals.
Antonio has signed a four-year deal with a further two-year option.
|Fan's view: David Blackmore, editor of West Ham United magazine Blowing Bubbles|
|"What a difference 24 hours can make! From frustration to jubilation. Very pleased with the re-signing of Alex Song on loan. I think he will thrive under Bilic and give our midfield some serious class.|
|"I'm also very excited about Victor Moses and Michail Antonio. They will both add to our pacey counter-attack and hopefully they will score a few goals, too.|
|"Jelavic wouldn't have been my first choice if I was looking to buy a striker from the Championship but we badly needed a striker and he has, at least, a history of scoring goals in the Premier League."|
Croatia international Jelavic has joined on an initial two-year contract with an option for a further two years.
Song returns to Upton Park after making 31 appearances for the club in all competitions during a loan spell in 2014-15.
Moses, who had loan spells at Liverpool in 2013-14 and Stoke last season, moves to West Ham on loan after signing a new four-year deal with his parent club.
The Hammers have allowed midfielder Matt Jarvis, 29, to join Norwich City on a season-long loan.
From non-league to Premier League
Londoner Antonio, who began his career at non-league Tooting & Mitcham United, has scored four goals in five matches for Forest this season.
"I can't wait for the challenge of playing in the Premier League," he told West Ham TV. "It was one of the things growing up - I wanted to test myself against the best.
"I've worked my way from non-league and finally got to the Premier League to show what I can do."
Antonio said his main attributes were "pace, power and goals".
"I came to a couple of games here when I was younger, so I'm happy to be finally here," he added.
Song returns to the Hammers
Song, meanwhile, joined Barcelona in 2012 from Arsenal for about £15m with a release clause of £63m (80m euros).
Having played 206 times for the Gunners between 2005 and 2012, he has made 39 appearances for Barca.
"It was a very easy choice for me to come back and I'm very happy to be here," he said.
"I feel at home and my family do too. They're set up very well here and my kids are playing for West Ham academy."
The Hammers have the option of extending Song's deal for a further season.
Moses leaves Chelsea for third time
Former Crystal Palace and Wigan player Moses moved to Stamford Bridge in August 2012, but has spent the past two seasons on loan.
"Delighted to sign a new deal at Chelsea and now looking forward to a good season with West Ham," he tweeted.
Jelavic reunites with Hammers boss Bilic
Jelavic's arrival at the Boleyn Ground sees him reunited with his former Croatia manager Slaven Bilic.
"I've played for Slaven before and he is a great manager and a great man. I am really happy and delighted to be working with him and all his staff again," said Jelavic.
The ex-Everton striker scored 16 goals in 54 Premier League appearances during a two-year spell at Goodison Park.
After a £6.5m move to Hull in January 2014, he scored a further 12 top-flight goals in 45 matches.
|More on transfer deadline day|
|10 ways to get a good deal on deadline day||The madness of transfer deadline day|
|The stories behind five panic buys||Peter Ridsdale's guide to deadline day|
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