Padraig Harrington and Darren Clarke are within striking distance of the summit after the opening round at the Senior Open Championship at Gleneagles.

Harrington, playing in his first Senior Open after turning 50 last August, is four under, two shots off the lead held by USA's Glen Day and Canada's Stephen Ames.

The three-time major winner, who missed the cut at the Open Championship at St Andrew's last week, is a recent first-time major tournament winner on the senior tour for players aged 50 and over, having won last month's US Senior Open.

Clarke bettered Harrington's round on Thursday by one stroke, with a five-under 65 which puts the Tyrone native in a tie for third, one off the leaders.

Day and Ames shot rounds of six-under-par 64, with both co-leaders recording an eagle - Day's coming at the par-5 18th to tie him with Ames as the first day of the tournament came to a close.

The pair lead by one shot over Clarke, Kent Jones, Jerry Kelly and Paul Broadhurst.

Harrington is in a group of seven tied at four-under alongside Ernie Els.

"I'm happy with the score," Harrington said.

"I putted well and my putter saved me most of the day."

Additional reporting: Reuters