Fears are growing for a missing British holidaymaker who vanished during a night out with friends hours after flying to the Algarve on Tuesday. Greg Monks' worried sister Jillian sounded the alert today, saying the Glaswegian had last been seen in the party resort of Albufeira during a first night out in the sunshine resort and describing his disappearance as 'completely out of character.' She wrote on an Albufeira expat site: 'My brother has not been since Tuesday evening. If you are currently there and have any information place contact me with any info.' Alison Meechan Fraser, from Hamilton, South Lanarkshire, subsequently confirmed the 38-year-old had been reported missing and police were looking for him. She said: 'He was with a group of friends. All the other boys are at the accommodation. 'They all arrived Tuesday, went on a night out and none of them have seen him since late Tuesday/early Wednesday. 'It's out of character, he's 38 and named Greg.' Jillian also confirmed her brother's disappearance had been reported to the British Embassy as well as police and his hotel. She said: 'Please any info. We are desperate. Not like him to do this.' Portuguese police could not be reached for an immediate contact this afternoon. MailOnline has contacted the UK's Foreign Office for comment. Other British holidaymakers reacted to Jillian's SOS by promising their support. Last month Edinburgh University history student Gregor Thomson vanished briefly less than a full day after arriving in Madrid with rugby club teammates for a weekend trip abroad. The 21-year-old's dad Murray touched down in the Spanish capital to learn his son had reappeared after becoming separated from friends during a night out.