Hugo Chávez returned to Venezuela early on Monday after more than two months of medical treatment in Cuba following cancer surgery.
Supporters of the ailing president staged street celebrations to welcome him home where he is now being treated at a military hospital in Caracas.
Chávez's return was announced in a series of three messages on his Twitter account, the first reading: "We've arrived once again in our Venezuelan homeland. Thank you, my God!! Thank you, beloved nation!! We will continue our treatment here." They were the first messages to appear on Chávez's Twitter account since 1 November. "I'm clinging to Christ and trusting in my doctors and nurses," Chávez said in another tweet. "Onward toward victory always!! We will live and we will triumph!!"
Chávez thanked Fidel and Raúl Castro, who have overseen his treatment in Cuba, and thanked his country's people "for so much love".
The vice-president, Nicolás Maduro, said on television that Chávez arrived at 2.30am and was taken to the Dr Carlos Arvelo military hospital in Caracas.
Chávez's return to Caracas came less than three days after the government released the first photos of the president in more than two months, showing him smiling alongside his daughters. The government did not release any images of his arrival in Caracas.
"We're very happy," Maduro said. He said he had accompanied the president on the journey, along with Chávez's daughter Rosa, his brother Adan and the national assembly president, Diosdado Cabello.
The vice-president said Chávez had been in a "continuous battle" and that additional details about his condition would be provided later.
Chávez supporters celebrated his return in central Caracas and outside the hospital. In Bolívar Plaza, a man holding a megaphone boomed: "Our commander has returned!"
Many in Cuba were taken by surprise by the news and wondered what it could mean about Chávez's health, details of which have been a closely guarded secret. The island nation depends on Venezuela for a steady flow of oil shipments.
Mirta Blanco, a 67-year-old retiree, said: "This could be good or it could be bad. I hope he's truly getting better, but I doubt it because what he has is irreversible. Maybe they sent him back to die. I think that's going to be his exit. It's huge news, but I think it's terrible."
There was no mention of his departure in morning newspapers, but Cuban state television described it as one of two "events loaded with emotion for Latin America" along with the re-election of the Ecuadorean president, Rafael Correa, on Sunday.
In a letter to Chávez read on state television and radio, Cuba's retired leader, Fidel Castro, said he was pleased that Chávez was able to return home.
"You learned much about life, Hugo, during those difficult days of suffering and sacrifice," Castro wrote. "Now that we will no longer have the privilege of receiving news of you every day, we will return to the kind of [written] correspondence we have used for years."
The government did not explain why Chávez made his surprise return on Monday. Government officials had in recent weeks said it was not clear when the president's medical team would allow him to travel to Venezuela, though they had said they hoped it would be soon.
The 58-year-old president has not spoken publicly since he left for Cuba on 10 December. He underwent his fourth cancer-related surgery the following day and the government says he is now breathing through a tracheal tube that makes talking difficult.
He has been receiving cancer treatment in Cuba on and off since June 2011. Chávez has said he has had tumours removed from his pelvic region and has undergone chemotherapy and radiation treatment. Neither he nor his government have revealed the type of cancer he has nor the exact location of the tumours.
Chávez was re-elected to a new six-year term in October. His inauguration had been scheduled for 10 January but was postponed indefinitely due to his condition after the surgery, which the government has described as delicate.