Spain tightened its grip yesterday on a barren rock, known as Parsley (Perejil) Island, just a stone's throw from the North African coast, and said its troops would only leave Perejil if Morocco promised not to occupy it again. A day after Spanish forces ousted six Moroccan soldiers from the isle in a bloodless raid, navy helicopters ferried equipment and men to the rock from nearby ships. Some 50 troops in combat fatigues built stone walls and dug in defences on the islet. Four Spanish warships sat in the bay as around 100 Moroccans and scores of journalists watched from overlooking cliffs some 200 metres (yards) away. Get out Spain! some locals cried, as others waved Moroccan flags and youths used sling-shots to hurl stones at Spanish Civil Guard launches darting near the Moroccan coast. Morocco claims sovereignty over uninhabited Leila, as it calls Perejil and sent soldiers to hoist its flag there last week. Spain also increased security at its enclave of Ceuta, some 6 km (4 miles) away, where riot police manned the streets. While Spain toughened its defences in North Africa, its new Foreign Minister Ana Palacio tried to calm tensions after Morocco had compared Wednesday's pre-dawn swoop by 28 members of Spanish special forces to a declaration of war. Obviously, this is not a declaration of war, Palacio told Spanish radio. We need to work to lower tensions. She reiterated that Spain would withdraw from the 13-hectare (30-acre) isle, at the mouth of the Straits of Gibraltar, once it had assurances Rabat would not try to occupy it again. Spanish Prime Minister Jose Maria Aznar said he would keep diplomatic channels open to Rabat in a bid to ensure a return to the status quo before Morocco occupied Perejil nine days ago. I have given instructions to keep up the necessary contacts with the Moroccan authorities to agree the terms which guarantee those aims, he said. Amid concerns the crisis could worsen relations between the Arab world and Europe, U.N. Secretary-General Kofi Annan offered to mediate in the dispute, but Spain said this was unnecessary. To talk about mediators in this crisis seems to me a bit foolish, Palacio told Spanish radio. This is something we have to resolve between Morocco and Spain. It is not sufficiently complicated for mediation. Spain wants a return to the status quo before Morocco's invasion of Perejil last week, but Rabat insists the islet forms part of its territory. The issue is highly charged due to the proximity to Ceuta. The future of Ceuta and Spain's other coastal enclave of Melilla is sensitive in the context of already torrid relations between Rabat and Madrid, marred by squabbles over immigration, fishing rights, oil exploration in disputed waters, and the future of the Western Sahara. Relations touched a low in October when Morocco suddenly withdrew its ambassador to Madrid, citing what it called a range of hostile attitudes towards Morocco. Talks between Britain and Spain over the disputed British colony of Gibraltar have prompted comparisons with Ceuta and Melilla by Rabat, which would like to absorb the two cities. There are things that can be discussed, but Ceuta and Melilla cannot be discussed, Palacio told BBC radio. Spain's Defence Minister Federico Trillo strongly rejected a Moroccan suggestion that Rabat and Madrid had been close to a preliminary U.S.-brokered deal to calm the situation before Spain's surprise raid. I wish it had been the case. The operation was so carefully planned that we could have suspended it five minutes before it was due to occur, but we saw no possibility of Morocco changing its position, he said.