Honolulu - Guam's governor urged residents to stay home and warned the island could take a direct hit from Typhoon Mawar as the storm strengthened on a path toward the U.S. territory in the Pacific.

Governor Lou Leon Guerrero urged residents in a YouTube message to remain calm and prepare for Mawar, which the weather service said could hit the southern part of Guam around midday local time on Wednesday.

'We may take a direct hit,' Patrick Doll, lead meteorologist for the National Weather Service in Tiyan, Guam, told The Associated Press. 'If we don't take a direct hit, it's going to be very close.'

The center of the Category 3 storm was about 313.8 kilometers southeast of Guam on Tuesday and moving northwest at 14.4 to 16 kph toward Guam, according to the weather service.

It was expected to arrive as a 225 kph Category 4 typhoon, weather officials said, possibly delivering the biggest hit in two decades.

The typhoon could cause 'extensive damage,' Doll said.

The governor said he would place Guam essentially in a lockdown effective 1 p.m. Tuesday.

'Unless you're a first responder, you do not leave your house,' Doll said.

Rain from the storm's outer bands was starting to fall Tuesday morning, he said.

A storm surge of 1.82 to 3 meters above the normal high tide was expected and could reach up to 4.6 meters. Surf was expected to build sharply in the next day or two along south- and east-facing reefs, with dangerous surf of 6 to 7.6 meters Tuesday afternoon into Wednesday, the weather service said.

At the island's grocery and hardware stores Monday, people were leaving with shopping carts full of canned goods, cases of water and generators, the Pacific Daily News reported.

The Guam Department of Education was preparing to open emergency shelters Tuesday, KUAM reported.

The Rev. Francis X. Hezel, a Jesuit priest and assistant pastor at Santa Barbara Church in Dededo, was trying to visit people at the hospital before it closed to visitors Tuesday.

Before hitting the road, he had trouble finding someone to help him put air in his tires because everyone was busy readying their homes to withstand the storm, he said.

'I live in a rectory,' he said. 'I'm just closing the windows, hoping that the gusts don't bash them in. Praying for the best, I guess.'

Officials warned residents who aren't in fully concrete structures to consider moving for safety. Many homes are made of wood and tin.

'The triple threat of a [category] 4 typhoon force winds, torrential rains and life-threatening storm surge are all expected for Guam and Rota,' the weather service said in a Tuesday morning update.

Rota, an island in the U.S. Commonwealth of the Northern Mariana Islands, was also under a typhoon warning, Doll said. Tinian and Saipan, in the northern Marianas, were under tropical storm warnings.

Some people in those areas are still in temporary shelters or tents after Category 5 Super Typhoon Yutu in 2018, Doll noted.

'Guam takes a Category 4 or 5 hit every five to seven years. Mother Nature has spared us as of late,' Doll said, adding that the last direct hit was in 2002. 'So we are way overdue.'