Indonesia's finance minister said the tax office will examine tax reports of the Indonesian offices of four Internet-based companies to check whether they have been paying correctly what they owe.

Minister Bambang Brodjonegoro named the four as Yahoo, Twitter, Google and Facebook.

While those companies have paid income taxes, they are still liable to value added tax applicable to revenue generated from advertising in Indonesia, he said.

Southeast Asia's largest economy is facing a sizable revenue shortfall this year as the resource-rich country can no longer rely on commodity-related income.

A decision to raise the threshold at which individuals start owing income tax in June, announced on Wednesday to boost economic growth, may aggravate the shortfall.

Out of the four companies, Yahoo and Google have formed Indonesian limited liability companies. Twitter and Facebook operate branches of their Asia-Pacific offices in Indonesia.

"Revenue from ads should be part of those taxable by us, we're doing a review," Brodjonegoro said, adding that Indonesia is demanding the same thing that Britain demands from those companies.

"The point is we will be serious in straightening up taxes on digital economy," he said.

The communications ministry has given an estimate of the value of digital advertising in Indonesia of about $800 million last year. But the ministry said all was untaxed.

Twitter is widely used in Indonesia, which is also home to the world's fourth-largest number of Facebook users.

Roy Simangunsong, Twitter's country business head for Indonesia, said he could not comment directly on the minister's statement, but said Twitter "will fulfill all obligations as a representative office in Indonesia".

An official at Google declined to comment before seeing the minister's statement and later could not be reached for comment.

Queries emailed to Yahoo and Facebook media officials were not answered.