Hollywood star Michael Douglas staged an impromptu walking tour of the Cuban capital's historic district, posing for photos with building workers and surprised residents.

His visit came two days after fellow Oscar-winner Sean Penn arrived in Cuba, reportedly seeking an interview with 82-year-old Fidel Castro, who has been little seen since announcing he was suffering from an unspecified illness in July 2006.

He stepped down as Cuba's president in February of the following year and was replaced by his brother Raul.

Penn travelled to the Isle of Youth, off mainland Cuba, on Monday to meet local artists. There was no word on whether he got to see Fidel Castro, but he interviewed Raul during a visit last year.

Little was known about Douglas' plans for his four days in Cuba, but he was accompanied on his walk through Havana's old quarter by Patricia Rodriguez, an official at the city historian's office.

Among the sites he toured was a state-run tobacco shop, where employees showed the actor the finer points of rolling a Cuban cigar.

It was unclear if either came with a US exemption to Washington's ban on travel to Cuba.