Islamabad, Sep 23 : Pakistan's weekly inflation spiked 38.66 per cent on a year-on-year basis, mainly due to a rise in petroleum prices, the Pakistan Bureau of Statistics (PBS) said on Saturday. The Sensitive Price Indicator-based inflation increased by 0.93 per cent for the week ending on September 21 as compared to the previous week, the PBS data revealed. The indicator comprised 51 essential items collected from 50 markets in 17 cities of the country, the PBS said, Xinhua news agency reported. During the week, out of 51 items, the prices of 22 items increased, 11 items decreased in price, and 18 items remained stable, the data showed. The PBS added that the prices of chicken, onions, garlic, petrol and diesel witnessed an increase during the last week. A decrease was recorded in the prices of sugar, bananas, tomatoes, wheat flour, cooking oil and tea, it said. /IANS