Mandela's condition continues to improve but remains serious JOHANNESBURG, June 13 (Xinhua) -- Anti-apartheid icon Nelson Mandela's condition "continues to improve but his condition remains serious," President Jacob Zuma said on Thursday. Zuma was speaking after visiting Mandela who has been hospitalized for a recurring lung infection since Saturday. Zuma, accompanied by African National Congress (ANC) Treasurer- General Zweli Mkhize, visited Mandela in hospital in Pretoria, the presidency said. "We continue to appeal to people to keep Madiba (Mandela) in their prayers and wish him a speedy recovery," said Zuma. Zuma said on Wednesday that Mandela "is responding better to treatment from this morning (Wednesday morning)." "We are very happy with the progress that he is now making, following a difficult last few days," Zuma said. Mandela, 94, was whisked from his Johannesburg home to hospital early Saturday morning after his condition deteriorated. As Mandela spent his sixth day in hospital, two of his daughters were seen entering the Mediclinic Heart Hospital where Mandela is receiving medical treatment. Mandela was visited by his daughters Zenani and Zindzi and their two children Zoleka and Zondwa, hospital sources said. Zindzi left the hospital after being at her father's side for an hour. Hope is growing that Mandela will continue to make progress after Zuma said he is responding well to treatment. With a heavy police presence, scores of people have been stopping by the hospital to wish Mandela well. A large contingent of local and international journalists are holding to their camping sites in front of the hospital, hoping to report the latest news about Mandela's condition.