West Ham have signed Czech Republic midfielder Tomas Soucek from Slavia Prague on loan with an option to buy.
Soucek, 24, has scored 10 goals in 19 appearances for Slavia this season and would cost the Hammers £13m.
Manager David Moyes said Soucek, who has 25 international caps, "fits the profile of the player we want".
Moyes, who replaced Manuel Pellegrini on 30 December, said on Tuesday the club had also submitted another bid, believed to be for a right-back.
West Ham are 17th in the Premier League table, outside of the relegation places only on goal difference.
"We are in a difficult period where we need experienced players," added Moyes, who is in his second spell at the club.
"At the moment he [Soucek] ticks a lot of boxes. We need to give him an opportunity and time to settle in."
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