Mystery has surrounded the horn-like noise that emerged from the River Clyde in the early hours of this morning.

Glaswegians from across the city were woken up to the blasts from the Clyde after an emergency signal sounded from a ship berthed at the Clydebank's fuel depot.

The 'general emergency' marine alarm signal – seven short blasts and one long blast from a ship's horn – could be clearly heard over the town shortly before 12.30am on November 20.

A coastguard rescue team was alerted a few moments later – but after investigations it turned out to be a false alarm from a ship which was safely tied up at the fuel depot at Rothesay Dock.

Catherine McColgan was one of several Twitter users who took to the social media platform to ask if anyone knew the source of the noise.

Eilidh McIntosh also tweeted: "Anyone know what that noise was? A boat horn on the Clyde? Felt like I was back in Orkney with the ferry coming in!"

The Greenock coastguard rescue team tweeted at 1.18am: "We can confirm that a vessel in the Clydebank/Erskine area had a malfunctioning distress system resulting in distress horns being activated around 00:30.

"Our operations centre have spoken with the vessel in question and can confirm she is safely alongside and in no distress."

And the medical transport charity Scotservs said one of its volunteer responders had phoned in the alert.

Twitter user @sjfiredragon said: "If you live in #Clydebank or #Dalmuir and got woken up 00:19 by a series of 7 short and 1 long boat horn blasts you can thank the #StenAurora for setting off its general emergency signal at the CB fuel depot!! Everyone fine, back to bed."