Shares in Saudi Aramco, the world's largest oil company, took a beating on Monday amid the oil price crash, with supermajors also seeing significant damage to their bottom line.

Aramco's shares slumped a further 10% on Monday as crude tumbled by as much as 30% in early trading in response to a decision by the Saudi government to abandon output restraints that have kept a floor under the oil market.

(Click here to read's Upstream's comment on Saudi Arabia's decision to trigger an oil price war.)

Crude futures, however, pared back some of the losses though both the global benchmark, Brent, and US futures were down 20% in afternoon trade.

Aramco shares fell below the company's initial public offering price on Sunday for the first time since the company was listed in December.

Shares were trading at 28.35 riyals ($7.56) after 1pm GMT on Monday, well below the 32 riyals per share at which the company launched its initial public offering.

The share plunge puts into serious doubt plans by the Saudi government to further reduce its stake in Aramco as part of a diversification of its oil-based economy.

Saudi Arabia has threatened to pump as much as 12 million barrels per day following the collapse of talks between Opec and non-Opec member allies, led by Russia, in Vienna on Friday.

Saudi Arabia is offering deep discounts to its major clients as part of a new strategy to regain market share lost to Russia and shale producers in recent years.

But the policy risks sinking the oil-dependent Saudi economy as well as causing social turmoil among a Saudi population long used to government handouts and subsidies.

Shares in major international oil companies also tumbled in London and New York. UK supermajor BP saw its shares plunge by 22%, while Anglo-Dutch supermajor rival Shell had 15% of its value wiped out.

US supermajors ExxonMobil and Chevron did not fare better, both losing 14% of their market value in early New York trading.

Analysts warned of further losses unless Saudi Arabia reverses its new policy of pumping at will.

"If Saudi maintains this course there is further downside as prices fall towards cash cost of production (likely in the mid-$20s)," Redburn Energy said.

"The length of time Saudi would willingly tolerate prices so far below its fiscal breakeven ($70 per barrel) is unclear, as is the potential response from Russia and US shale. It is clear that the oil price correction will exert substantial pressure on the majors’ financial frameworks," it said.

Both Iran and the United Arab Emirates are hopeful that renewed contacts with Russia will lead to a breakthrough in salvaging an alliance that has helped sustain oil prices in the past three years.