MEULABOH, Indonesia (AFP) - Bereaved families across Asia wept and prayed on Friday as they marked four years since a huge tsunami devastated the shores of the Indian Ocean in one of the worst ever natural disasters. Thousands gathered in fields, on beaches and by mass graves to commemorate the disaster that killed around 220,000 people when walls of water smashed into coastal communities, where many people are still homeless. In Indonesia's Aceh province, the heaviest-hit region with at least 168,000 people killed, crowds massed in the shattered remains of a military base in the coastal town of Meulaboh for a sombre prayer ceremony. "We are here to remember the martyrs who were killed in the tsunami and to give us momentum to rebuild a better Aceh," local government head Ramli Mansur told the crowd. "The four-year anniversary of the tsunami holds deep meaning, because right here we witnessed the first place the waters of the tsunami came into Aceh," he said. Sariani, a tearful 20-year-old street vendor, recalled the moment the waves hit, trapping her and her family in their house from which only she and her husband and daughter managed to escape. "I came here to remember my beloved mother, my son and my brothers and sisters who were killed in the tsunami," she said. Around 50 tsunami survivors, left homeless after the disaster, chanted and waved placards after the ceremony, demanding housing and accusing authorities of failing to look after victims. Prayers were held in mosques throughout the staunchly Islamic province, including tearful ceremonies at mass graves in the tsunami-devastated capital of Banda Aceh and along the province's coastline, local media said. Indonesia also marked the anniversary with tsunami drills at the northern end of the sprawling island of Sulawesi and on Java island, local media reported. In Sri Lanka, the country that suffered the second highest death toll from the tsunami, the government asked people to observe two minutes of silence in memory of the victims. Religious services were held across the island's coastline for the estimated 31,000 people who perished there in the disaster. Officials said the government's new disaster management authority had by Friday commissioned 25 out of 50 tsunami early warning towers planned after the disaster. In India special prayers and memorial services were held in coastal villages in the southern state of Tamil Nadu, where an estimated 6,500 people perished in the tsunami. Women cried and beat their chests during memorial services for the dead in fishing villages that were devastated by giant waves. Many survivors said they had not been provided permanent houses, while some complained about the quality of construction. "We have not yet got our promised tsunami houses," said Ku Bharathi, president of the South Indian Fishermen Welfare Association. "I can't understand why government officials give false interviews to newspapers claiming that 7,300 houses have been built." In Thailand, where 5,400 people were killed, half of them foreign tourists, hundreds of people gathered along the country's southwest coast to place wreaths, float lanterns and release sea turtles to commemorate the disaster. In the tourist hotspot of Phuket, around 1,000 residents and tourists gathered on the main Patong beach, with three other events held elsewhere on the island. Thousands of candles were to be lit and placed in coconut shells along a three-kilometre (two-mile) stretch of Kamala beach, south of Patong, in a ceremony attended by foreign Minister Kasit Piromya, a provincial official said. Recovery has been uneven across the countries hit by the tsunami, despite a massive outpouring of billions of dollars in international aid. In Indonesia, 6.7 billion dollars of a pledged 7.2 billion dollars in aid has already been spent but many survivors remain homeless. Ongoing fighting between Tamil separatists and the government in Sri Lanka has hampered rebuilding there, with 10,000 people still living in camps.