Footballer Fabrice Muamba can now "breathe independently" and has been able to recognise family members and respond to questions, his club has said.
The 23-year-old remains in intensive care at the London Chest Hospital after collapsing during an FA Cup match on Saturday but Bolton Wanderers Football Club said in a statement on its website that he was continuing to show signs of improvement.
A joint statement by the club and the hospital trust said: "Fabrice Muamba remains in intensive care at the London Chest Hospital. He is continuing to show signs of improvement this evening.
"He is currently able to breathe independently without the aid of a ventilator. He has also been able to recognise family members and respond to questions appropriately.
"These are all positive signs of progress. However, his condition remains serious and our medical staff in intensive care will continue to monitor and treat him.
"His family and club would like to thank the media for continuing to respect their privacy at this time."
It was also confirmed that his heart started beating without the aid of medication and he had begun to move his arms and legs of his own accord after spending two days in hospital.
An earlier joint statement from Barts and the London NHS Trust and Bolton said his long-term prognosis would remain unclear for some time.
Curtis Codrington, a friend who has visited the player, said: "Fabrice is speaking and moving. He has spoken minimal words in French and English."
Muamba collapsed on the pitch at 6.11pm as Bolton Wanderers played Tottenham Hotspur at White Hart Lane during an FA Cup quarter-final clash.
Dr Andrew Deaner, a distinguished cardiologist, ran to his aid moments after he fell to the ground in front of millions of fans who watched on television.
Paramedics desperately tried to resuscitate him but it was almost two hours before medics were able to get the midfielder's heart beating on its own.
Today, a string of visitors from the football world - including Chelsea defender Ashley Cole, QPR's Shaun Wright-Phillips and former team-mate and Arsenal player Johan Djourou - arrived at the hospital to offer their support.
Bolton Wanderers manager Owen Coyle and chairman Phil Gartside also stopped by as Muamba's family urged fans to pray for the player.
His brother, fiancee and colleagues have visited the footballer since he was admitted, the Press Association reported.
Outside the hospital - where fans have left tributes - Coyle said relatives had been "inundated" with messages of support.
"We all know he's such a wonderful lad, he's a young man and we all hope that will help in this brave fight which he is undergoing at the moment," he said.
"It's a difficult situation but the family are bearing up as well as they can. They themselves are very positive people.
"You look at what Fabrice has been through in life already and you can tell that he is a fighter.
"He has such a fantastic smile and that's what we all want to see again."
Meanwhile, Sunderland boss Martin O'Neill praised the speed with which Muamba was treated.
He said: "I only reiterate how quickly things were dealt with at White Hart Lane.
"That can only be really good news."
Muamba's fiancee, who goes by the name Shauna Muamba on Twitter and is mother to their son Joshua, has left a series of messages on the social networking site.
"God is in control. Please keep @fmuamba in ur prayers xx," she wrote.
She later added: "Please keep praying for @fmuamba its really helping I can feel it xx".
Another post read: "2 everyone out there thank u so much for all the love and support collectively as a family we appreciate it all. Plz continue 2 pray 4 fab x."
On Valentine's Day she told followers she had accepted the player's marriage proposal.
His club has postponed its next fixture - a Premier League tie against Aston Villa - which was due to take place tomorrow evening.
Meanwhile, Blackburn manager Steve Kean said he was happy for next weekend's match at Bolton to be postponed if Wanderers felt they were not ready to play.
"I think the whole footballing world has come together," he said.
"Whatever we have to do, we would only respect what Bolton want us to do next weekend.
"We hope he makes a full recovery but if they need a little bit more time and the game doesn't go ahead, then we would respect that from Bolton's point of view."