Four lions at a Singapore wildlife park have tested positive for the coronavirus after coming into contact with infected zookeepers, and have symptoms including coughing and sneezing, officials said Wednesday.

The endangered Asiatic lions started displaying signs of illness at the weekend, prompting officials to order coronavirus tests.

The infected big cats along with five others at the Night Safari park have been placed in isolation in their den, the government's animal and veterinary service said.

"All the lions remain bright, alert and active," said Sonja Luz, from Mandai Wildlife Group, which operates the park.

"We expect that the lions will make a full recovery with minor supportive treatment."

Three zookeepers from the Night Safari are confirmed to have been infected. The park is an open-air zoo home to hundreds of animals, which welcomes visitors at night.

An African lion at Singapore Zoo -- which is adjacent to the Night Safari -- has also fallen sick, and officials have ordered virus tests.

Luz added the risk of animals passing the virus to humans is low. 

Both Singapore Zoo and the Night Safari remain open, although the lion exhibits have been temporarily closed.

Animals have become infected with the virus on previous occasions. Lions, tigers and gorillas have tested positive at US zoos, while domestic cats and dogs have also been hit.

Singapore is currently facing its worst Covid-19 outbreak since the start of the pandemic, reporting 2,000-3,000 cases a day and a handful of deaths.