Red Sea attacks shake oil marketsKazakhstan adds to supply concernsJust weeks after crude prices had fallen on hopes that the Middle East was easing, oil has staged a sharp comeback. Fresh attacks on Saudi oil tankers in the Red Sea and a disruption to Kazakhstan's exports have revived fears over global supplies, sending prices beyond the $100-a-barrel mark.On Friday, Brent crude futures fell 63 cents, or 0.63%, to $100.1 a barrel, while US West Texas Intermediate (WTI) crude slipped 69 cents, or 0.75%, to $91.50 a barrel. Despite the decline, Brent remained on track for a 13.5% weekly gain, while WTI was set to rise 10.9%.In the previous session, Brent settled 7% higher and WTI gained 6.2%. Brent also closed above $100 a barrel for the first time since May and touched $102 during the session, its highest level since then.The latest rally comes after Iran-aligned Houthi rebels said they had attacked two Saudi oil tankers in the Red Sea.The attacks raised concerns that the Bab el-Mandeb shipping route, which links the Red Sea to the Indian Ocean, could face disruptions. He also warned of "major military punishment" against the Houthi rebels in Yemen if they continued attacking ships.