The second attack happened in Alexandra Park, Glasgow

In the first incident on Friday, a cygnet was found with a crossbow bolt in its shoulder after being shot in Maryhill.

Then following an early morning attack on Tuesday, a swan was found in Alexandra Park with three crossbow arrows still in its body.

Police described the latest attack as a "dangerous act of barbaric cruelty".

A Strathclyde Police spokesman said Tuesday's incident happened at about 0630 BST.

It is the worst instance of deliberate cruelty of any wildlife I've seen in 30 odd years Andy Christie Hessilhead Animal Rescue

The swan was discovered by a park ranger and is now being cared for at Hessilhead Wildlife Rescue Centre, Beith.

It had one arrow in its side, one in its breast and a third which went in through its right hip with the tip coming out of its left hip.

Although the bird has a broken wing, it is hoped it will recover fully.

Andy Christie, co-founder of the rescue centre, told the BBC Scotland news website: "We were warned it was going to be unpleasant but it is the worst instance of deliberate cruelty of any wildlife I've seen in 30-odd years.

"This was three deliberate aimings," he said. "The person who did this must have seen the other two arrows sticking out when he shot the swan for a third time.

This swan has a broken wing but is now recovering from its ordeal

"This is someone who is pretty sick and who should be taken out of circulation."

Insp James Kirkland said: "This was a dangerous and barbaric act of cruelty and I am appealing to the public to assist us in apprehending those responsible.

"The public will rightly be outraged that wildlife within their park has been targeted in such a callous manner and I would ask for their full co-operation."

The cygnet injured on Friday was captured by the Scottish SPCA and spokeswoman Doreen Graham said it had been "very lucky".

"These are serious incidents and these birds have suffered," she said. "Someone has planned to shoot these birds to hurt them. It's just mindless.

"Crossbows are dangerous to people as well. Anyone who sees someone carrying a crossbow in Glasgow please ring the police."

Anyone with information can contact London Road police office on 0141 532 4617 or Crimestoppers on 0800 555 111.