Oil prices ended a tumultuous week on a positive note even as the US Federal Reserve cut interest rates and President Donald Trump announced additional tariffs on $300 billion worth of Chinese goods. Brent futures for October settlement closed at $61.89 per barrel on Friday, while West Texas Intermediate finished at $55.19 per barrel after taking a hit following Mr Trump’s decision on China. WTI, which tracks North American crude grades, plunged to its worst performance in a single day in four and a half years after the White House announced 10 per cent tariffs on $300bn worth of imports from China. The decision stoked fears of a further escalation in a trade war between the world's largest oil producer and importer. Trade tensions between the two largest economies have already exerted a bearish sentiment on oil markets, keeping prices in check despite rising geopolitical tensions in the Middle East. “Volatility will likely remain high as the market gets a feel for potential Chinese retaliatory measures in the coming days, while the more medium term macro situation has taken a hit with the chances of a swift US-Chinese rapprochement diminishing,” JBC Energy said in a recent note. The White House’s latest measures against Beijing follows an earlier decision to levy a 25 per cent duty on around $250bn worth of goods from China. President Trump wrote on Twitter on Thursday: "...during the talks the US will start, on September 1st, putting a small additional Tariff of 10% on the remaining 300 Billion Dollars of goods and products coming from China into our Country. This does not include the 250 Billion Dollars already Tariffed at 25%…" His tweet sent the oil markets into a tailspin, with Brent losing 7 per cent of its value to plunge to $60.50 on Friday, before recovering the following day. Markets remain on guard for Chinese reaction to the latest tariffs, after Beijing vowed to retaliate. "China will have to take necessary countermeasures to resolutely defend its core interests,” foreign ministry spokeswoman Hua Chuying said on Friday. “We don’t want to fight, but we aren’t afraid to,” she added. China is the world's largest importer of oil and second biggest purchaser of liquefied natural gas, which it considers a transitional fuel as it pursues a greener economic growth agenda. Beijing has already increased tariffs on imports of the super-chilled fuel from the US to 25 per cent from 10 per cent. The production of gas from US shale basins is booming and it is one of the fastest growing exporters of LNG in the world, soon to rank behind Australia and Qatar as one of the world's top producers for the fuel. Any increase in tariffs by China, which has imported two cargoes of LNG from the US this year, would be a huge blow to America's ambitions of gaining market share in the sector. On Sunday, Iran's Islamic Revolutionary Guard Corps announced the seizure of another tanker in the Arabian Gulf for abetting fuel smuggling in the region. The Iranian state news agency ISNA, which reported the seizure, did not disclose details on the identity of the vessel. Last month, Iran seized the British-flagged <em>MT Riah</em>, which had set sail from the UAE emirate of Sharjah, on the same charges. The tanker was suspected to have been captured off Iran's Larak Island, with the IRGC releasing video footage matching the vessel's attributes. A day later, Iran impounded the British-flagged and Swedish-owned <em>Stena Impero</em> on charges of attacking one of its fishing vessels. The seize followed threats of retaliation against the capture of a tanker carrying Iranian crude off the coast of Gibraltar by the British Royal Marines.