Caracas:
Venezuelan President Hugo Chavez flew to Cuba on Saturday to undergo a fourth round of radiation therapy to treat a recurrence of cancer.
State television showed Chavez boarding a Havana-bound plane at Simon Bolivar International Airport at 8.00 pm local time (0030 GMT Sunday).
"We will continue our battle, and we will continue winning," the Venezuelan leader tweeted shortly before take-off. A heartfelt embrace to my beloved and heroic people. We will keep living and keep winning."
The Venezuelan President said earlier his trip to Cuba would last several days.
Under the constitution, Mr Chavez is required to seek permission from the National Assembly if he is to stay outside the country for more than five days.
The announcement of Mr Chavez's return to Cuba, however, came only two days after he arrived home from the island late on Wednesday after completing a third course of radiation therapy.
The left-wing firebrand had timed his return to Venezuela to participate in events that commemorated his return to the Presidency after being briefly removed from power 10 years ago during a coup.
Mr Chavez had surgery in February in Havana after the return of the cancer that he was originally diagnosed with in 2011.
He has been undergoing treatment after the removal of a malignant tumor in the same pelvic area where another such tumor was removed in June 2011.
Officials in Caracas have never specified the type of cancer the President has or exactly where it is, but insist it has not spread to other organs.
In addition to battling cancer, he is also running for a third six-year term as President in the October 7 election. He faces a tough reelection against the youthful united opposition candidate Henrique Capriles.