Hong Kong (CNN Business) Hackers in China have significantly stepped up attacks on US companies as the two countries have clashed over trade and technology.

Top cybersecurity firm CrowdStrike saw "a big resurgence" last year in efforts by China-based groups to break into the systems of American businesses for commercial gain — a trend that "shows no sign of stopping," said Michael Sentonas, the company's vice president of security technology.

The spike in attacks on US targets — which include telecom operators, pharmaceutical firms and hotel chains — is "likely tied to increased tensions between the two countries," CrowdStrike said in a report published Tuesday.

Chinese attacks on US companies had fallen away in recent years after the two governments agreed in 2015 not to conduct cybertheft of trade secrets and intellectual property against one another for commercial gain. That drop-off now "appears to have been reversed," CrowdStrike said.

ZTE ZTCOF Tensions between the United States and China escalated sharply last year as Washington slapped heavy tariffs on huge swathes of Chinese exports and cracked down on some of the country's top tech companies, including Huawei and. Cybertheft is one of the key US complaints against China in the dispute over trade and technology.