European natural gas futures extended gains in after-hours trade on Monday as renewed conflict in the Middle East heightened concerns over further disruptions to global liquefied natural gas supplies through the Strait of Hormuz.
The front-month Dutch TTF contract rose 5.960% to 51.555 euros ($58.72) per megawatt-hour, while the UK front-month NBP contract gained 6.408% to 124.70 British pence ($1.67) per therm.
The rally followed escalating military exchanges between the US and Iran, raising concerns over the security of the Strait of Hormuz, a key energy transit route.
Conflicting claims over the waterway's status added to uncertainty, with the US saying it remained open and Iran claiming it had been closed "until further notice," Trading Economics said.
US President Donald Trump further fueled concerns after he posted on X that the US would take control of the strait and be reimbursed "at the rate of 20% on all cargo shipped" for overseeing the vital passage.
He posted that the US will be known as "the guardians of the Hormuz Strait" going forward.
Supply concerns have raised questions over Europe's ability to rebuild gas inventories before winter.
LNG imports fell by more than 15% over the year in the first eight days of July after declining 18% in June, ANZ analyst Daniel Hynes said, citing Kpler data. He added that stronger Asian demand is likely to intensify competition for LNG cargoes in the coming months.
Gas Infrastructure Europe said EU gas storage facilities were 51.84% full on Monday, versus 62.63% a year earlier and the 67.2% five-year average reported by the Swiss Federal Office of Energy.
However, the European Commission's Energy Union Task Force said Friday that gas prices remain well below 2022 energy crisis peaks and there are no immediate concerns over winter supplies.
It added that EU storage is on track to meet seasonal filling targets, while spare LNG import capacity should provide additional flexibility during the heating season.
Celsius Energy said European gas inventories currently stand at 1,994 billion cubic feet as of July 11, 594 Bcf below the five-year average.
It projects storage will peak at around 2,760 Bcf by Oct. 31, equivalent to roughly 71% of Europe's total storage capacity of 3,914 Bcf, leaving inventories 729 Bcf below the five-year seasonal average.