Tax officials in Kazakhstan, an oil-rich Central Asian country, Friday questioned the legality of production sharing agreements signed with foreign oil and gas companies.
"We have analyzed production sharing agreements signed earlier. There are questions on the way the agreements were drawn up," the Interfax news agency quoted the head of the finance ministry's tax committee, Daulet Yergozhin, as saying.
Officials have "questions on the legality of the signing of certain contracts," Yergozhin was quoted as telling journalists in Astana.
"We are working on them at the moment, and we have until April 1 to submit proposals to the government," Yergozhin said, without specifying which agreements were being reexamined.
The announcement came after President Nursultan Nazarbayev called in January for changes to favourable tax terms granted to Western oil companies when they signed production sharing agreements in the 1990s.
Even though the Kazakh authorities have not named any particular agreements, the move is likely to raise concerns among major oil and gas companies operating in the country.
Kazakhstan, a former Soviet republic in Central Asia located between China and Russia, is rich in natural resources including crude oil, gold and uranium. Western investors have flocked to the country since independence in 1991.
But the climate for foreign investors has worsened in recent months and the authorities have accused Western oil majors such as ENI and Chevron of failing to respect contracts for some of the biggest new oil fields in the world.
This would not be the first time that Kazakhstan has forced multinational companies to revise their contracts to provide Astana with more favourable terms.
After a long fight, Kazakhstan managed to considerably increase its stake in Kashagan, considered the world's largest oil field to be discovered since the 1960s. At full capacity, it will produce 1.5 million barrels of crude oil per day.