Bangladesh on Friday moved two warships to confront an alleged 'intrusion' by three Indian vessels, for hydrocarbon exploration in its territorial waters, in the resource-rich Bay of Bengal.

The move came after the Bangladesh Navy protested the incident and the government ordered a probe, following which 'appropriate' action will be taken.

"We have already lodged a ship-to-ship protest while the Indian vessels still remain in our territory," a Navy official said.

A news agency, quoting Foreign Ministry officials, said that one survey vessel backed by two Navy ships intruded for hydrocarbon exploration.

"We will file a diplomatic protest note by Saturday to get the Indian vessels to go away," Foreign Secretary Mohammad
Touhid Hossain said.

Bangladesh Navy frigate Khalid bin Walid and another battleship were sent to the scene on Thursday night. Officials claimed that they asked the Indian ships to back off as the survey vessel apparently entered the 'disputed waters'.

Foreign Adviser of the interim government Iftekhar Ahmed Chowdhury said an investigation had been ordered.

"We are investigating the matter and will take whatever action is deemed appropriate on the basis of the results of the investigation," Chowdhury told PTI.

Maritime officials earlier said the Indian vessels started their exploration activities some 140 nautical miles southwest off Mongla seaport.

The incident came a month after a similar row broke out between Bangladesh and its neighbour Myanmar, after a South Korean firm escorted by Myanmarese ships started exploration work off its coast.

After a military standoff with mobilisation of warships in Bay of Bengal and troops in their borders by the two countries, they held talks on maritime boundary, but it ended inconclusively.

Bangladesh and India held three-day talks in October this year after a gap of 28 years.

Dhaka and New Delhi [Images] at that time agreed to hold further talks in the near future to settle the maritime dispute, as they could not reach a consensus on the mid-flow of the cross-boundary Hariabhanga River, considered crucial for demarcation of maritime border.

The Foreign Ministry, later in a statement, said that Bangladesh would lodge a formal protest with New Delhi.

"The government of Bangladesh is lodging a formal protest with the government of India about the activities of the survey ship in Bangladesh waters," it said.

It said Dhaka would ask for the postponement of any "exploratory or development activity in adjoining areas till such time as the maritime boundary between the two countries is settled by mutual agreement."

A foreign ministry spokesman said an Indian survey ship was seen conducting survey in the deep sea block 14, in the maritime area claimed by Bangladesh, under its Territorial Waters and Maritime Zones Act 1974.

He said the survey ship was escorted by two other 'support vessels', adding that a Bangladesh Navy patrol vessel at the scene asked the Indian ship to leave Bangladesh waters.

The spokesman said the survey ship initially moved towards Indian waters but "later came back to the earlier location, where they were again located in the afternoon of 25 December 2008".

"When our Navy vessel again asked it to leave Bangladesh waters, the ship replied that it was in Indian waters," he said.