June 8 (Reuters) - Democratic Republic of Congo has issued invoices to telecoms operators under a new tax that is expected to cost them around $180 million per year, two sources familiar with the matter said on Wednesday.

The government adopted the tax imposing levies on every phone call, text message and megabyte of data in March. Telecoms companies operating in Congo include Airtel, Vodacom , Orange and Africell.

The tax replaced another levy that was withdrawn a month earlier after sparking public protests and a parliamentary inquiry into where the revenues were going.

The Congo Authority for Post and Telecommunications Regulation (ARPTC) issued an order earlier this year blocking price increases on consumers, meaning the burden of the new tax will fall on the companies.

The national chamber of commerce said in a statement on Tuesday that the levy threatened to squeeze a telecoms sector whose taxes are already far higher than the average in sub-Saharan Africa.

"All the operators in Congo have rejected these invoices, judging them to be tarnished by irregularities and thus unenforceable," it said.

The invoices cover a period of roughly six weeks and come to about $20 million, one of the sources said, asking not to be named.

A government spokesman referred a request for comment to the ARPTC, which could not be immediately reached. Representatives for the telecom companies were not available to comment. (Reporting by Aaron Ross and Nqobile Dludla; editing by Barbara Lewis)