SINGAPORE (Reuters) - Singapore refused entry to an Australian man charged under his country’s terrorism laws over his past activities, authorities said on Thursday, days before the Southeast Asian nation hosts a historic summit of U.S. and North Korean leaders.

The wealthy city-state has been stepping up security measures in the run-up to Tuesday’s summit between U.S. President Donald Trump and North Korean leader Kim Jong Un.

Zeky Mallah, 34, was the first person charged in 2003 under Australia’s new terrorism laws, accused of planning a suicide attack on the offices of the Australian Security Intelligence Organisation and the department of foreign affairs, Singapore’s Ministry of Home Affairs said in a statement.

He was later acquitted of two charges of preparing a terrorist act in 2005, but received a 2-1/2-year jail sentence after pleading guilty to threatening violence against Australian government officials, it added.

Zeky arrived on Wednesday from Sydney and was put on the next available flight back to Australia, leaving on Thursday.

Others denied entry to Singapore include two Muslim preachers banned last year, with authorities saying their views bred intolerance and were a risk to social harmony.