Dhaka - Dhaka has protested the alleged intrusion into its territorial waters of three Indian ships to carry out hydrocarbon exploration activities in the Bay of Bengal, reports said Friday.

Foreign ministry officials said the Bangladesh government followed the protest Thursday night by sending a naval frigate to the area, demanding the Indian ships return to their own waters.

In a statement issued later in the day, Dhaka called on New Delhi to postpone exploration activities in the disputed waters until the maritime boundary is settled by mutual agreement.

"The government of Bangladesh is lodging a formal protest with the government of India about the activities of the survey ship in Bangladesh waters," a foreign ministry statement added.

It said that an Indian Survey ship was seen conducting survey in the deep sea block 14 in the maritime area claimed by Bangladesh in terms of Territorial Waters and Maritime Zones Act 1974. The survey ship was aided by two support vessels.

The statement said the Bangladesh Navy vessel asked the Indian ship to leave Bangladesh waters, but after it initially moved towards Indian waters, it came back to the earlier location where they were deployed on Thursday afternoon.

Bangladesh Foreign Secretary Touhid Hossain earlier said he had information that Indian ships entered Bangladesh waters.

The Indian survey vessels started seismic survey activities some 140 nautical miles south-west of Mongla seaport, a Bengali language newspaper reported, quoting a navy source.

The alleged intrusion comes ahead of Bangladesh's general elections, slated for Monday.

Bangladesh has yet to demarcate its maritime boundary in the mineral-rich Bay of Bengal with its neighbours - India and Myanmar - making it difficult to conduct oil and gas exploration.

India and Myanmar have already offered international oil giants rights for mineral exploration in their territories, which Bangladesh says partly overlap its own territorial waters.

In November, tension rose between Dhaka and Yangon over Myanmar's attempts to explore oil and gas in waters disputed by Bangladesh, prompting the two sides to send warships to the bay.

After almost two weeks of disagreement over offshore oil and gas exploration, the two sides agreed to stop mineral searches in the disputed waters until an agreement is signed finalising the demarcation of the maritime boundary between Bangladesh and Myanmar (dpa)