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.

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.

The Chinese government has repeatedly denied any involvement in cyberattacks.

Even after US President Donald Trump and Chinese leader Xi Jinping agreed to a truce in the trade war in December, the American government continued to pressure Beijing on cybertheft.

The US Justice Department charged two Chinese nationals in late December, accusing them of participating in a global hacking scheme to steal business secrets as part of a campaign allegedly directed by the Chinese government. Following the indictments, the Chinese Foreign Ministry urged the US government to "stop smearing China on cybersecurity and withdraw the so-called charges against Chinese nationals to avoid causing serious damage to China-US relations."

The intensified US pressure on Huawei has also strained relations between the two countries. Washington is pushing American allies to ban Huawei from participating in super-fast 5G networks , saying its equipment could be used by the Chinese government for spying. US prosecutors have also brought charges against Huawei and one of its top executives over alleged bank fraud and sanctions evasion.

Huawei rejects the claims that its products pose a security risk and denies all the US charges.

Hackers in China are showing particular interest in targeting telecommunications operators around the world, according to CrowdStrike. That's a sensitive issue a time when many governments, under pressure from the United States, are debating whether using Huawei equipment in next-generation wireless networks poses a security risk

Telecommunications operators are a popular target for hackers because they "have an amazing amount of information" on the general public and other organizations like governments and businesses, Sentonas said.

Companies in the hospitality industry come under frequent attack for similar reasons, he added.