HONG KONG—Two of Hong Kong’s largest consumer retail chains started rationing some food and drug items on Friday to curb panic buying that has plagued the city over the past week amid fears of a citywide lockdown as COVID-19 cases soar. Supermarket chain ParknShop announced limits of five items per customer on staples such as rice, canned food and toilet paper while pharmacy Watsons put the same limits on medication for pain, fever and colds, Hong Kong media reported. On Wednesday, ParknShop announced shorter opening hours, with some of its 200 branches shutting at 3 p.m.—by which time many shops across the Asian financial hub have been stripped of fresh and frozen meat and vegetables in recent days. Both ParknShop and Watsons are units of the Hong Kong listed conglomerate, CK Hutchison. Hong Kong officials have repeatedly urged people against panic buying this week, saying supplies were adequate. Amid public …