Leaders of the world's biggest economies begin a two-day G20 summit on Saturday in India's capital of New Delhi.

As India hosts such a powerful group of world leaders for the first time, New Delhi has been adorned with ornamental flowers and fountains at traffic roundabouts, with a fresh coat of paint for public buildings and sidewalks were spruced up.

Security is being provided by 130,000 police and para-military troops, along with anti-drone systems and cutouts of langurs to scare off monkeys, while stray dogs have been cleared from the streets.

WHAT IS THE G20?

The world's 20 major countries formed an economic grouping after the Asian financial crisis in 1999 on the understanding that crises spilling across borders needed better international economic co-operation to tackle them.

The bloc accounts for 80% of global gross domestic product (GDP) and 75% of international trade.

It includes Argentina, Australia, Brazil, Britain, Canada, China, France, Germany, India, Indonesia, Italy, Japan, South Korea, Mexico, Russia, Saudi Arabia, South Africa, Turkey, the United States and the European Union.

Although only treasury chiefs met in initial years, the heads of all member nations decided to meet once a year for a summit after the 2008 financial crisis.

The G20 is discussing a plan for the African Union to join.

WHAT ARE THE KEY ISSUES THIS YEAR?

India's year-long presidency has seen discussions centre on issues such as more loans to developing nations by multilateral institutions, reform of international debt architecture, regulations on cryptocurrency and the impact of geopolitics on food and energy security.