Mumbai: The BSE benchmark Sensex on Monday plunged to an over four-months low, losing 364 points on across the board selling on emergence of reports that government might impose capital gain tax on investments routed through Mauritius.

A weakening trend in Asia and lower opening in Europe on the European Union's decision to delay Euros 12 billion aid to Greece until it passes austerity package at home also fanned market fears of Greece's sovereign debt  default in the mid of July.

The Bombay Stock Exchange index, Sensex, which had lost over 438 points in the last three trading sessions, plunged by another 363.90 points to  7,506.63, the levels last seen on February 9.

Further, during the intra-day trade, the gauge had dipped by 556 points, with most of the stocks recording steep losses.

Broad based National Stock Exchange's 50-share index Nifty nosedived by almost 109 points to 5257.90 level.

Trading sentiment turned bearish on major sell-off by funds and retailers on reports that the government will sought to tax capital gains on investments made through Mauritius.

Sensex leader RIL fell nearly four per cent to a 52-week low of Rs 829 a piece.

The markets already weak after hike in interest rates and reports of lower advance tax collection for the first quarter this fiscal, received another jolt after BSE announced on Friday that Anil Ambani group companies stocks—Reliance Infra and Rcom will be removed from the Sensex by August 8.     Reliance Infra sank 6.07 per cent to Rs 545.25 and Rcomby 7.89 per cent to Rs 87.60 on fresh selling.

Among sector indexes, the realty sector index suffered the most, losing 4.16 per cent to 2,016.49 followed by Oil and Gas index that dwindled by 3.42 per cent to 8,6568.42.

The IT sector index plunged by 2.50 per cent to 5,673.38 as Tata Consultancy Services dropped 3.69 per cent to 1,069.55 on reports the software maker has been ordered to pay Rs 6.56 billion in back taxes after tax officials denied some of its claims.