Zimbabwe's former leader Robert Mugabe has been in hospital in Singapore for four months, his successor President Emmerson Mnangagwa has said.Mr Mnangagwa said the 95-year-old "founding father of our nation" had been receiving treatment for an undisclosed ailment and was responding well.In a statement released on Monday, he added: "Unlike in the past when the former president would require just about a month for this, his physicians this time around determined that he be kept under observation for much longer from April this year when he left for his latest routine check-up."President Mnangagwa had announced in November that Mr Mugabe was unable to walk because of ill-health and old age.When the government announced in April that he had gone to Singapore for medical treatment, it said that he was expected back home in mid-May.Mr Mnangagwa said he had sent a team to Singapore last week to check on the former ruler, and that "because of the good progress he is making Mugabe could be released fairly soon".Zimbabwe's public health services have practically collapsed and those who can afford it seek treatment in South Africa or further abroad.Mr Mugabe during his time in power sought almost all his medical care in Singapore.Mr Mnangagwa, who took over in November 2017 with the backing of the military - ending Mr Mugabe's 37-year rule, went on to be elected in disputed elections in July last year.