TAIPEI, July 25 (Reuters) - Taiwan cancelled parts of its annual military drills on Tuesday as authorities step up preparations for what they say could be the most damaging typhoon to hit the island in nearly four years.

Typhoons are common at this time of year near Taiwan but the subtropical island has not been directly hit by a typhoon since 2019, prompting officials to urge vigilance.

Typhoon Doksuri, ranked a category four super typhoon on a scale of 1 to 5 by Tropical Storm Risk, is expected to enter the Bashi Channel that separates Taiwan and the Philippines in a west-northwesterly direction and approach waters off the island's southern coasts before making landfall in southern China, weather officials said.

Taiwan's defence ministry cancelled parts of the main annual Han Kuang exercises scheduled for Tuesday, citing safety concerns and the need to make preparations for the coming storm.

Taiwan's weather bureau has issued sea warnings and said it will issue land warnings for its southern counties later on Tuesday, urging residents there to prepare for heavy rains and strong winds.

"Taiwan has not seen any typhoon making landfall in more than 1,400 days, and that's why I urge all government ministries that they must gear up and make preparations," Premier Chen Chien-jen said in a post on Facebook.

"I'd like to remind citizens not to underestimate the typhoon threats."

It was not immediately clear how the typhoon could further impact the five-day military drill, which is set to take place throughout the island this week and focus on defending the island's main international airport and how to keep sea lanes open in the event of a Chinese blockade.

In the southern port city of Kaohsiung, authorities were rushing to collect hundreds of containers drifting on the sea after Palau-flagged container ship Angel sank off Taiwan's southwestern coast last week.