Bangladesh has suspended operations of three private phone operators in less than a week for allegedly running unlicenced phone services, a spokesman of the telecom regulatory body said Friday.

The Bangladesh Telecommunications Regulatory Commission closed the offices of Ranks Telecom Ltd, or RanksTel, a private firm licensed in 2004 as a public switched telephone network (PSTN), as the government was convinced that the operator runs an illegal business using Voice over Internet Protocol (VoIP), for which it is not licenced.

'We have shut down all activities of RanksTel since Friday morning after we found a huge quantity of VoIP equipment at the company's office,' BTRC chairman Zia Ahmed said, adding that three employees had also been detained.

On Wednesday, authorities discovered evidence of illegal VoIP operations at the offices of WorldTel Bangladesh Ltd, which has been running PSTN operations since 2000. The phone operator was also switched off, the BRTC chairman said.

Five top officials of Dhaka Phone, another PSTN operator, were arrested Monday on a similar charge. The company's operations were suspended.

There are nine private operators running PSTN services across Bangladesh beside the state-run Bangladesh Telecom Ltd, providing service to some 1.6 million subscribers.