The Briton has 4,138 points after four events with the Belgian second (4,042) and Kendell Williams third (3,855).

The 26-year-old won her 100m hurdles race in 13.09 seconds - taking 0.21secs off her previous best.

Her high jump was 1.95cm before 13.86m in the shot put - a 71cm improvement.

Johnson-Thompson then ran 23.08 in her 200m heat to regain the lead going into the final three disciplines on Thursday.

"To end the day on top is really important," Johnson-Thompson told BBC Sport. "I've still got three events to negotiate but to end the day on top after a not great 200m, I'm happy to be on top."

The Liverpool athlete's day-one advantage over Thiam is a slight improvement on last year's European Championships, where the lead was 87 points, although Thiam went on to win the title by 57 points.

Following the shot put, British Sydney 2000 champion Denise Lewis told BBC Sport: "We've seen her face so glum for so many years so to conquer it here is just fantastic. She is demonstrating that she is a competitor. She is ready."

Dame Jessica Ennis-Hill, Britain's former world and Olympic heptathlon champion, said she was impressed by Johnson-Thompson's start to the competition.

"That's how you want to begin a heptathlon," said the 33-year-old. "She got into her running and halfway down the track you saw her get into her rhythm.

"I almost thought Thiam was going backwards, but Kat was just pulling away from her."

Disappointment for Miller but joy for McKinna

It was a disappointing men's hammer final for Briton Nick Miller. He came into the event ranked fourth in the world, but the Carlisle-born 26-year-old only managed 75.31m as he finished 10th.

He later lodged an appeal against a foul given for his second throw of the evening, which if successful could have propelled him into a medal spot.

However a jury panel upheld the decision to call a foul throw.

Elsewhere, Great Yarmouth's Sophie McKinna celebrated wildly as she booked her place in Thursday's shot put final with 18.61m - the sixth best effort in qualifying and nearly 40cm better than her previous best.

"I'm never speechless but I am speechless now," said the 25-year-old, who celebrated by running across the track.

"As a thrower, you generally know when you let go of it if it's a good throw. I didn't expect that.

"To get into a final and perform to the best of my ability at a World Championships - it means the world.

Laura Muir eased into the 1500m semi-finals, while fellow Scot Eilish McColgan was another member of the Great Britain team to impress as she qualified for Saturday's 5,000m final as fourth fastest with a time of 14 minutes 55.79 seconds - fewer than eight seconds shy of her personal best.

Team-mate Laura Weightman, trained by former world champion and BBC commentator Steve Cram, was fifth in her heat and also made it through, however Jessica Judd missed out.

Defending champion Hellen Obiri of Kenya was the fastest qualifier.

McLeod's title defence ends with fall

Grant Holloway races to victory after defending champion Omar McLeod clattered to the ground

In the men's 110m hurdles final, Jamaica's defending champion Omar McLeod fell as he looked to challenge leader Grant Holloway over the final set of barriers.

The 21-year-old American stayed on his feet to win in 13.10 seconds. Russian 2015 champion Sergey Shubenkov, competing as an Authorised Neutral Athlete, took silver and French European champion Pascal Martinot-Lagarde won bronze.

British world indoor 60m hurdles champion Andrew Pozzi, who only recently returned to racing after two months out, had earlier failed to qualify for the final.