The Philippines is to deploy hundreds of riot police to the holiday island Boracay to keep out tourists and head off potential protests ahead of its six-month closure to visitors.

Rodrigo Duterte has described the tiny central island and its white-sand beach as a “cesspool”. The Philippine president ordered visitors to be kept away from 26 April to enable facilities to treat raw sewage to be set up and illegal structures to be torn down.

On Tuesday, authorities unveiled a lockdown plan to keep out all foreign and Filipino tourists using more than 600 police officers, including a 138-person “crowd dispersal unit”.

Speaking at a public forum aired on national television, Ch Supt Cesar Binag, the regional police director, said: “In any transition, especially for a drastic action such as this, there is always confusion, uncertainties and low morale.

“What we did was to identify the sources of confusion, sources of uncertainty and sources of low morale that might result to agitation and eventually into a security issue.”

Boracay residents will be obliged to carry new identification cards and will be banned from boating and night swimming, he said.

Entry to the 1,000-hectare (2,470-acre) island, located 186 miles (300km) south of Manila, will be limited to one small seaport.

Island residents’ identity cards are expected to be distributed three days before the shutdown, and security forces will conduct a “capability demonstration” next week, Binag said.

Businesses in the area, which previously lobbied for a phased rehabilitation, have warned that an abrupt shutdown could lead to bankruptcies and job losses for many of the island’s 17,000 hotel, restaurant and other tourism workers, plus 11,000 construction workers.

The island attracted 2 million visitors last year, earning the country more than $1bn (£700m) in tourism revenue, according to official data.

The abrupt decision to close Boracay forced hundreds of hotels, restaurants, tour operators and other businesses to cancel bookings.

The threat of closure first emerged in February, when Duterte accused Boracay’s businesses of dumping sewage directly into the island’s turquoise waters. “I will close Boracay. Boracay is a cesspool,” he said in a speech in his home city of Davao.

The government maintains that it is legal to deploy police and bar tourists from the island.