Oil prices traded sideways on Friday and were on track to end the week above $100 per barrel for the first time in nearly four months as supply concerns from the Middle East rose after Houthi rebels seized a key port city along the Red Sea and ships continue to come under attack in the Strait of Hormuz.Brent, the benchmark for two-thirds of the world's oil, was down 2.31 per cent to $105 a barrel at 11.16am UAE time. West Texas Intermediate, the gauge that tracks US crude, was trading 1.96 per cent lower at $100.5 a barrel.Oil prices edged higher early in the morning after touching $109 per barrel in the previous session. Oil, however, pared gains later in the day.“Prices jumped as Houthi forces advanced towards coastal areas near the strategic Bab Al Mandeb Strait, including a push towards Mokha, raising fears of deeper disruption to Red Sea shipping,” Soojin Kim, a Dubai-based analyst at Japanese lender MUFG, said.“The escalation compounds existing pressure on Gulf supplies, with Houthi attacks earlier in the week forcing some Saudi energy facilities to halt operations while US-Iran fighting continues to threaten tanker traffic through Hormuz.”Houthi rebels on Thursday seized Mokha, a key port city along the Red Sea near Bab Al Mandeb Strait that is critical for Saudi Arabia’s oil flow to Asian markets. The new development has raised fears that the Yemen-based group could increase its influence along the strait and disrupt oil exports that could further tighten oil markets and put upward pressure on prices.Play01:09What's happening in Bab Al Mandeb?Ship traffic hits another lowPreliminary data from Kpler shows ship traffic across the Bab Al Mandeb strait reduced on Thursday, with 27 vessels crossing the key chokepoint for global crude, down from 32 the previous day. Of the total, 16 exited the Red Sea, while 11 entered. A Russia-flagged vessel exited the sea carrying about 791,000 barrels of crude towards the Indian port of Sikka. Vessels were also going towards Singapore, Bangladesh, China and Indonesia.Strait of Hormuz ship traffic also remains thin as the US and Iran engage in tit-for-tat attacks on oil tankers.Earlier this week, the US military destroyed five Iranian oil tankers, while Iran said it retaliated by attacking 10 ships near the key channel.Only seven vessels crossed the Strait of Hormuz on Thursday, down from 12 on Wednesday and 18 on Tuesday, according to Kpler. More than 100 vessels used to transit the route, carrying 20 per cent of global crude and liquefied natural gas supplies, before the conflict in February. “The key question for oil markets is no longer whether Brent can break above $100. It already has,” said Priyanka Sachdeva, an analyst at Phillip Nova. “The question now is whether the market can stabilise below $120, or whether another wave of supply disruption pushes crude into a completely new price regime.”Global benchmark Brent crude touched an intraday high of $126.41 per barrel on April 30, marking a four-year high as a result of the Iran war and its impact on supplies.Saudi production has also fallen sharply amid constraints on both its Gulf and Red Sea export routes, which is supporting oil prices.