Former Prime Minister Dr Mahathir Mohamad is making "significant progress" after undergoing surgery for a chest infection following a recent heart bypass, doctors said today.

Mahathir, 82, is undergoing physiotherapy after surgery on Saturday for the infection following the bypass operation on Sept 4.

The former premier, whose first heart bypass procedure was in 1989, was taken off a ventilator on Wednesday, the National Heart Institute said.

"He is now breathing on his own since 2 pm yesterday (Wednesday) and doctors are now focusing on post surgical rehabilitation," the institute said.

"These include physiotherapy to his chest to optimise his respiratory function as well as exercises to his arms and legs to build muscle strength," it said in a statement.

Mahathir remains in intensive care in hospital.

Grilling the doctors

"Yes he is making good progress. I thought he looked pretty good, for someone in ICU," said his daughter, Marina, in her web blog.

"Apparently he spent time last night grilling the doctors! I'm not sure many patients get to do that but as he sometimes likes to sniffily remind us 'I'm a doctor too, you know'!" she said.

Despite retiring from office in 2003 after 22 years in power, Mahathir, a general practitioner before entering politics, remains an influential figure.

He has become an outspoken critic of his handpicked successor, current prime minister Abdullah Ahmad Badawi, accusing him of economic mismanagement, nepotism and corruption.