With global stocks at all-time highs, investors can't shake off the fear factor

Global markets hit record highs this week as the frenzy around artificial intelligence boosted risk sentiment and hopes of a return to economic growth. But some investors have urged caution, suggesting that high tech valuations could put the rally at risk.

Oliver Bäte, CEO of wealth manager Allianz, which has around $1.85 trillion in assets under management, said it looks "very dangerous out there."

"We are very cautious about some of the valuations in the tech sector," he told CNBC's "Squawk Box" Friday.

European markets extended gains Friday after the Stoxx 600 index closed at an all-time high in the previous session.

Fresh earnings out of Europe and spillover from Nvidia's bumper revenue report in the U.S. helped push the pan-European benchmark to 495.1 Thursday — surpassing its previous record of 494.35 in Jan 2022, according to LSEG data. Germany's DAX and the French CAC also hit record highs.

In Asia Pacific, Japan's Nikkei 225 closed at a new all-time high of 39,098.68 on Thursday, surpassing the previous record of 38,915.87 set in 1989.

The gains have been mirrored stateside, with U.S. stock indices also scaling fresh all-time highs.

It comes amid ever-growing hype around AI innovation and the anticipated boost it could bring to the sluggish global economy.

Shares of Nvidia closed up 16% Thursday after its full-year results showed revenues jumped 265% on the back of soaring demand for its AI chips. The surge boosted Nvidia's market cap by $276 billion — the biggest one-day gain for any company on record.

Standard Chartered CEO Bill Winters told CNBC Friday that the recent rallies pointed to AI "innovation in action on every front," and said his company had benefited "enormously" from the tech. The comments came shortly