Tsang cautioned members of the public to be alert to such attacks, before "any real catastrophe" happens. The veteran officer, with years of experience in criminal investigation, expressed concern over cases in which homemade bombs were found in a secondary school and residential areas, and of police arrests of criminal groups who had been testing explosives.
Trump has also criticized Germany for paying Russia "billions of dollars" for energy with their Nord Stream 2 gas pipeline project.
Trump has angered Democrats with his comments describing some immigrants as criminals, verbal attacks on black professional athletes protesting against racism and Twitter slaps at female politicians.
Trump took a dig on Tuesday at Nadler and House Intelligence Committee chairman Adam Schiff, one of the president's strongest critics in Congress about the Russia investigation.
Trump made the announcement in an Oval Office address to the nation as he seeks to combat a viral pandemic.
Trips to four nations to boost traditional friendships, implement consensuses
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Trump, who will surely be watching at the White House, has strongly denied any quid pro quo, and has bashed the diplomats by saying that none of them had firsthand knowledge of his thinking.
Trump pardons 15, including Republican allies - World - Chinadaily.com.cn
Trump said there might be travel restrictions beyond China, to other hard-hit countries such as South Korea and Italy.
Trump signed the Coronavirus Aid, Relief and Economic Security (CARES) Act into law last March authorizing the payments. The parties disagree on the extension of higher unemployment benefits, delaying action.