Indonesian rescuers worked on Thursday to save a pod of beached whales that got trapped in a mangrove swamp at low tide, fisheries officials said.

Villagers in the area in the east of Java island were helping fisheries staff trying to lead the 30 or so whales, most of which were believed to be young pilot whales, back to sea.

Several of the whales had died after being hurt in the shallows and many of the others were weak, officials said.

"The residents are trying to push the active whales back toward deeper water ... but some are still stuck," Deddy Isfandi, a fisheries official in the coastal town of Probolinggo, told media.

Another fisheries official, Wahid Noor Azis, told Reuters seven of the whales were calves while the biggest of the adults was up to four metres (13 feet) long.

The officials said they did not know why the animals ventured into the mangrove swamp. Residents said whales were rarely seen in the area.

Whale beachings, while unusual, have been seen in other parts of Indonesia.

This year, a four-tonne, 16-metre (52 foot) sperm whale was found dead on a beach on the resort island of Bali.