Military forces have seized power in the South American nation of Suriname, ousting an 18-month-old civilian government in a bloodless coup, the Dutch news agency ANP reported Tuesday.

The reported overthrow came one week after the head of the armed forces and former military ruler of the former Dutch colony, Desi Bouterse, resigned his post in protest over his temporary detention in Amsterdam.The acting commander of Suriname's armed forces, Ivan Graanoogst, announced the military takeover at 10 p.m. EST Monday on Surinamese television, saying an interim government would be formed to lead the country until free elections sometime before April 1991.

The coup overthrew the 18-month-old civilian government of President Rameswak Shankar, of the Hindu-backed Progressive Reform Party, who was elected by the National Assembly Jan. 12, 1988.

Shankar's administration had replaced the military government led by Bouterse, a Netherlands-trained lieutenant colonel who seized power Feb. 25, 1980 to depose the civilian regime of Prime Minister Henck Arron.

Bouterse lost an election to Shankar in 1987.

Ongoing friction between the two men came to a head last week when Dutch police temporarily detained Bouterse in Amsterdam during an airline stop en route to Ghana, and Shankar, who was on the same plane, refused to intervene.

Bouterse subsequently resigned as chief of the armed forces in protest.

Although Bouterse has not headed the government in 18 months, he has continued to exert a strong influence over developments in the country.

Graanoogst's position remained unclear, but observers said he appeared to be acting in the interests of Bouterse.

Communications with Suriname following the reported coup Monday night appeared to have been cut off, and repeated attempts to contact the Paramaribo, the capital of the former Dutch colony, were unsuccessful.