Bangladesh mobilised three warships and said it would take "all possible measures" to protect its territory Monday after accusing neighbouring Myanmar of encroaching on its seawaters to hunt for gas.

Bangladesh will also send a high-level delegation to Myanmar to "defuse" tensions between the two countries, according to a statement issued by the foreign ministry.

Bangladesh's foreign minister Iftekhar Ahmed Chowdhury said he had warned Myanmar's envoy to Dhaka that "all steps would be taken to protect the sovereignty and territory of Bangladesh."

The Bangladesh Navy warships took up position near disputed waters in the Bay of Bengal to face off with the Myanmar exploration fleet, top navy officials told an AFP correspondent in southeastern port city of Chittagong.

"Myanmar navy deployed four civil ships with survey team and equipment of a Korean exploration company at the front side at the disputed waters backed by its two warships from behind," an official said.

"We are observing the situation and have urged Myanmar navy to pull back their ships in a bid to ease tension," said a navy official. "We are on high alert."

On Sunday, Bangladesh summoned Myanmar's envoy to hand over a "strong protest note" over the reported intrusion of vessels to look for oil. The area in question has not been demarcated and both countries claim it as their own.

The Myanmar embassy in Dhaka said it had no official comment.

Myanmar has discovered huge reserves of natural gas in the Bay of Bengal and has expressed its intention to carry out further exploration in a stretch of the sea also claimed by Bangladesh.

The two countries have held a series of meetings in the past year aimed at resolving the disputes over the maritime boundary, including a meeting last month in Dhaka of senior ministers from both countries.

Early this year Bangladesh divided its sea territory into 28 blocks and auctioned off the area to international oil companies as part of its efforts to end chronic gas shortages in the once gas-rich country.

Myanmar immediately protested the move.

Meanwhile, Bangladesh's border security forces said that four Bangladeshi woodcutters were killed after trespassing into Myanmar.

Colonel Naim of Bangladesh Rifles (BDR) told AFP the woodcutters' mutilated bodies had been found late Sunday by relatives two kilometres (1.2 miles) inside Myanmar at the foot of a hilly pass.

The two countries share a 90-kilometre unfenced border along hilly and porous terrain.

"We don't know whether they were killed by the Myanmar border forces or local people from Myanmar, but it appears that the four bodies had been tossed over a hill about 1,000 feet (300 metres) high," said Naim, who uses only one name.

He said the bodies were badly disfigured and officials in Bangladesh would be contacting border forces in Myanmar as part of their investigation into the killings.

"We have never had such deaths along the Bangladesh-Myanmar border before," he said.