India Inc. experienced a drastic downfall in mergers and acquisitions in 2011, partly due to the global downturn. According to preliminary data from Dealogic, India's targeted volume decreased 33 percent to $ 43.7 billion in 2011 from $ 65.1 billion in 2010.

Following are the top five M&A deals in India:

Reliance-BP Deal

Reliance sold their shares to London-based BP for $ 7.2 billion. BP took 30 percent shares in 23 oil and hydrocarbon basins operated by the Reliance Industries. The companies said they would start a joint venture to buy, transport and sell oil.

Vodafone Essar-Vodafone Group Deal

Vodafone Essar sold 33 percent of its shares to UK-based Vodafone group for $5.4 billion. Vodafone group raised 74 percent and Essar owns 22 percent of stakes.

Adani Enterprises-Abbot Point Coal Terminal Deal

Adani Enterprises bought majority of shares from Abbot Point Coal Terminal, an Australian-based for $1.9 billion. The deal will help ship out huge amount of coal from Australia. Adani group said the deal was to acquire one of the largest ports in the world.

Essar-Royal Dutch Shell Deal

Essar Company invested $1.2 billion on Royal Dutch Shell. Essar is a multinational conglomerate company in various sectors like energy, power, steel and telecom.

The company's main goal is to expand globally in oil & gas sector. It has already bought shares in Africa and owns 50% of shares in Kenya Petroleum Refines Ltd in Mombasa, Kenya. It has over 1,600 oil retail outlets in India.

Hancock Coal - GVK Power& Infrastructure Deal

GVK Power Infrastructure has bought 79 percent of stakes from Hancock Coal Pvt for $1.2 billion. GVK said they hold majority coal resources, railway line and port infrastructure from Hancock, an Australian-based company. According to the contract, the company will receive 20 million tonne of coal every year.