Former Pope Benedict is “absolutely lucid and alert” and his condition is serious but stable, the Vatican has said.

The update comes a day after Pope Francis said his predecessor Benedict XVI is “very sick” and asked the faithful to pray for the retired pontiff so God will comfort him “to the very end”.

Vatican spokesman Matteo Bruni said: “The Pope Emeritus was able to rest well last night. He is absolutely lucid and alert today, although his condition remains serious, the situation at the moment is stable. Pope Francis renews his invitation to pray for him and accompany him in these difficult hours.”

Pope Francis did not elaborate on Benedict’s condition as he made the surprise appeal for people to pray for him at the end of his general audience yesterday.

The Vatican said after the service that the 95-year-old’s condition had suddenly “worsened due to age”.

A Vatican spokesperson said he was receiving constant medical care and his condition was “under control”.

Benedict became the first pope in some 600 years to resign in 2013, with the former pontiff taking the title pope emeritus.

Since then, he has been living in the Vatican.

He has become increasingly frail in recent years after dedicating his post-papacy life to prayer and meditation.

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Pope asks for prayers for Benedict XVI

Some cardinals and canon lawyers have questioned Benedict’s decisions on retirement, including his decision to continue wearing the white cassock of the papacy.

Another point of contention has been Benedict refusing to revert back to his birth name Joseph Ratzinger.

Critics say those choices and Benedict’s continued presence in the Vatican have been confusing for Catholics and threaten the unity of the Church.

Traditionalists have been able to use Benedict as a conservative point of reference when they’ve been unhappy with Francis’s decisions, they say.

Benedict resigned in 2013 due to his “deteriorating” health.