Britain's FTSE 100 rebounds, GKN gains after results

* Blue-chip FTSE 100 index rises 0.4 percent

* Energy and mining shares among top gainers

* GKN (LSE: GKN.L - news) advances 2.3 percent after results

By Atul Prakash

LONDON, Oct 21 (Reuters) - Britain's top share index rose on Tuesday, with gains for engineering firm GKN after results and in drugmaker Shire (Xetra: S7E.DE - news) on merger speculation supporting the broader market.

GKN rose 2.3 percent after saying it was on track for growth in 2014 following a 6-percent rise in third-quarter profit, driven by its aerospace and automotive units.

"The update is no worse than expected. Good growth for the company's automotive business in China was reported, whilst overall management outlook comments proved to be broadly supportive," Hargreaves Lansdown (LSE: HL.L - news) analyst, Keith Bowman, said.

"In all, given the group's diversity and ongoing momentum, analyst opinion remains highly favourable in tone," he said.

Shire rose 2.7 percent with traders cited a Reuters report, based on two sources familiar with the matter, saying Allergan shareholder Paulson & Co was urging the firm to merge with Shire as an alternative to a deal with hostile bidder Valeant Pharmaceuticals.

The FTSE 100 was up 0.4 percent at 6,293.17 points by 0832 GMT after falling on Monday.

Commodity stocks were in demand, with the oil and gas index up 1.4 percent and the mining index up 0.6 percent, tracking stronger oil and metals prices.

Brent crude oil rose to about $86 a barrel on news of robust Chinese oil demand, while copper gained on hopes of more stimulus measures from China after it reported a slowing of third-quarter economic growth to its weakest since the 2008/09 global financial crisis.

Growth in the world's No. 2 economy cooled to 7.3 percent between July and September from a year earlier, slightly above the 7.2 percent forecast by analysts.

"The stronger close on Wall Street and better-than-expected readings on Chinese GDP is helping to buoy stocks," H2O Markets chief market strategist, Mike Jarman, said.

"Value investors who still believe in the global macro backdrop along with strong Apple (NasdaqGS: AAPL - news) earnings should keep market sentiment positive. I expect stocks to post gains across the board this week," he said.

Late on Monday, Apple forecast a strong holiday quarter after a better-than-expected 16-percent jump in iPhone sales and the strongest growth in Mac computer shipments in years helped it beat Wall Street's targets. (Editing by Louise Ireland)