Shares in miners rebounded as investors looked for bargains following recent falls in the sector.
Sentiment was also helped by upbeat economic data from China - the world's largest importer of raw materials.
BHP Billiton rose 3.3% and Rio Tinto was 3% higher. The two firms topped the FTSE 100's risers board, with the index up 28.67 points at 6,715.24.
Shares in the London Stock Exchange rose 2.2% after it reported a 16% rise in half-year operating profits to Â£239.4m.
The group's results were boosted by the contribution from the US Frank Russell business, which it bought last year and combined with its own FTSE index business.
Legal & General shares rose 1.8% after the insurer reported an 18% rise in operating profits to Â£750m in the first half of the year.
Ryanair shares were up 1.6% after the company said that in July it became the first airline to carry more than 10 million passengers in a month.
Ryanair said it carried 10.1 million customers last month, up 11% from a year earlier.
On the currency markets, the pound rose 1.6% against the dollar to $1.5589, and climbed 0.3% against the euro to â‚¬1.4350.

Bates, who has been Tigers promoter for three years, has taken full control of the Lions and will work alongside co-promoter David Darcy.
Bates said: "We're only weeks away from the new season and so our main priority is to quickly form a team.
"We have opened talks with several riders and should be in a position to announce the first signings any day."
Lions endured a miserable season last time out and finished bottom of the Elite League table.
But Bates said he hoped the club's financial difficulties were a thing of the past.
"I am aware that Leicester went through a difficult trading period last season," he said.
"And I will be doing everything possible to ensure that the club is placed on a sound financial footing that secures the future of Leicester Speedway for years to come."

The poster with the phrase #prayforjosh appeared in Holywood by the A2 within the last week.
It is part of a social media campaign supporting 13-year-old Joshua Martin, from Donaghadee, County Down.
Life took a dramatic turn for the teenager when he was diagnosed with cancer on Christmas Eve.
He was due to have an operation on his appendix at the Royal Victoria Hospital in Belfast.
However, doctors instead discovered and removed a large primary cancer and five smaller growths.
The news shocked Josh's family, but since his diagnosis they have received lots of support from people all over the world.
It began as a hashtag on Facebook and Instagram by Bangor Elim Church, where Josh's father is on the pastoral staff, and has since gone viral.
The church's senior pastor, Gary Beattie, said he was amazed by how many people have supported Josh and his family so far.
"We were in total shock when he was diagnosed, and really the family just wanted support from people and to ask people to pray for Josh," Gary said.
"It certainly isn't a campaign as such, we just put the hashtag on our Facebook posts to get some of our congregation thinking about him. We had no idea that it would take off.
"We would use social media quite a lot because we have quite a young congregation, and we've been posting updates about Josh from his family.
"The update was shared 948 times and it's been seen by over 79,000 people. It's absolutely phenomenal.
"We thought there had been a mistake, but you can look at the views and where they've come from, and there are people all over the world supporting him, which is great."
But how did a social media hashtag lead to the appearance of the massive billboard?
Gary said that last week a mystery donor paid for the sign and it was erected at Holywood playing fields.
"We do not know where it came from, we didn't put it there, but it means a lot to have such support," Gary said.
There has also been a huge outpouring of support on Twitter for the Bangor Grammar pupil, with his classmates using the now-global hashtag for their friend.
As Josh's family and friends continue to support him in his recovery, it now seems there will be people all over the world will be following suit, thanks to the kindness of County Down strangers.
(Noon): The market remained in positive territory during lunchtime trade, with mining shares among the top risers.
[NEXT_CONCEPT]
Leicester Lions Speedway have been bought by Sheffield Tigers promoter Damien Bates.
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A large billboard has been puzzling residents of a County Down town, and commuters on the main route between Bangor and Belfast.