Oil prices extended gains, after rising a dollar a barrel in the prior session, as investors braced for a worsening of the Middle East crisis, potentially involving Iran, the third-largest oil producer in OPEC, Reuters reports.

Brent crude futures advanced by 30 cents, or 0.3 per cent, to $90.78 a barrel by 0325 GMT, while US West Texas Intermediate crude futures rose 25 cents, or 0.3pc, to $86.46 a barrel.

Both contracts rose more than 1pc in the prior session after three sons of a Hamas leader were killed in an Israeli airstrike in Gaza, feeding worries that ceasefire talks between the two sides might stall.

Earlier this week, Israel and Hamas began a fresh round of negotiations in their more than six-month-old Gaza conflict but those discussions have yielded no agreement.