(Adds sales details, stores opening)
April 26 (Reuters) - Britain's biggest pizza delivery firm Domino's Pizza Group said first-quarter sales rose 18.3 percent as strong trading around the New Year and Easter, and online orders helped offset the impact of unusually colder weather.
Sales at UK stores open over a year rose 7 percent in the quarter, picking pace from 4.8 percent growth seen in 2017.
UK online sales rose 16.2 percent year-on-year to contribute nearly 80 percent of system sales in the quarter, Domino's said.
Domino's, which has 1,054 stores in the UK but also operates in Ireland, Switzerland and Germany, said group system sales in the 13 weeks to April 1 rose to 311.1 million pounds ($433.6 million).
The London listed company, a master franchisee of U.S. group Domino's Pizza Inc, said it opened nine UK stores in the period and remained on track to open 65-75 new stores in 2018.
Dominos said 541 out of its 1,054 stores in the UK had GPS tracker functionality, allowing customers to track their deliveries.
Much like its parent company, Domino's Group is also focusing on sales through online channels to fend off competition from the likes of Just Eat, online food delivery company, which has sprung to the blue chip index in less than four year since listing. ($1 = 0.7174 pounds) (Reporting by Rahul B in Bengaluru; Editing by Gopakumar Warrier)